Common use of No Fiduciary Relationship Clause in Contracts

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby Each of Diamond Growers and Diamond Foods acknowledges and agrees that (i) the Underwriters are acting solely as underwriters purchase and sale of the Securities pursuant to this Agreement, including the determination of the public offering price of the Securities and any related discounts and commissions, is an arm's-length commercial transaction between Diamond Foods, on the one hand, and the several Underwriters, on the other hand, (ii) in connection with the offering of contemplated hereby and the Public Securities. The Company further acknowledges that the Underwriters are process leading to such transaction each Underwriter is and has been acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a principal and is not the agent or fiduciary to the Companyof Diamond Growers or Diamond Foods, or its management, stockholders, creditors creditors, employees or any other person party, (iii) no Underwriter has assumed or will assume an advisory or fiduciary responsibility in connection with any activity that the Underwriters may undertake or have undertaken in furtherance favor of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, Diamond Growers and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views Diamond Foods with respect to the price offering contemplated hereby or market for the Public Securitiesprocess leading thereto (irrespective of whether such Underwriter has advised or is currently advising Diamond Growers or Diamond Foods on other matters, do not constitute including any advice or recommendations rendered by Xxxxxxx Xxxxx relating to the Company. The Company hereby waives and releases, Conversion pursuant to the fullest extent permitted by lawletter agreement, dated January 17, 2005, between Xxxxxxx Xxxxx and Diamond Growers) and no Underwriter has any claims that the Company may have against the Underwriters obligation to Diamond Growers or Diamond Foods with respect to the offering contemplated hereby except the obligations expressly set forth in this Agreement, (iv) the Underwriters and their respective affiliates may be engaged in a broad range of transactions that involve interests that differ from those of Diamond Growers and Diamond Foods, and (v) the Underwriters have not provided any breach legal, accounting, regulatory or alleged breach of any fiduciary or similar duty tax advice with respect to the Company in connection with offering contemplated hereby and each of Diamond Growers and Diamond Foods has consulted its own legal, accounting, regulatory and tax advisors to the transactions contemplated by this Agreement or any matters leading up to such transactionsextent it deemed appropriate. If the foregoing correctly sets forth the is in accordance with your understanding between the Underwriters and the Companyof our agreement, please so indicate in the space provided below for that purposesign and return to Diamond Growers a counterpart hereof, whereupon this letter shall constitute instrument, along with all counterparts, will become a binding agreement between usthe Underwriters, Diamond Growers and Diamond Foods in accordance with its terms. Very Truly Yourstruly yours, PETRA ACQUISITIONDIAMOND WALNUT GROWERS, INC. By: Name: By _________________________________ Title: Agreed to and AcceptedDIAMOND FOODS, INC. By _________________________________ Title: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX CONFIRMED AND ACCEPTED, as of the date first above written: XXXXXXX LYNCH, PIERCE, XXXXXX & XXXXX INCORPORATED By _________________________________ Title: XXXXX XXXXXXX & CO. INCBy _________________________________ Title: XXXXXX XXXXXXX CORP. By _________________________________ Title: For themselves and as Representatives of the several other Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLCA hereto. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorA

No Fiduciary Relationship. The Company Western Gas Parties and the Selling Unitholder hereby acknowledges acknowledge that the Underwriters are acting solely as underwriters in connection with the offering purchase and sale of the Public SecuritiesUnits. The Company Western Gas Parties and the Selling Unitholder further acknowledges acknowledge that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis basis, and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the CompanyPartnership Entities the Selling Unitholder, its their management, stockholders, security holders or creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering purchase and sale of the Public SecuritiesUnits, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the CompanyPartnership Entities and the Selling Unitholder, either in connection with the transactions contemplated by this Agreement or any matters leading up relating to such transactions, and each Western Gas Party and the Company Selling Unitholder hereby confirms its understanding and agreement to that effect. The Company Western Gas Parties, the Selling Unitholder and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, transactions and that any opinions or views expressed by the Underwriters to the Company Partnership Entities and the Selling Unitholder regarding such transactions, including including, but not limited to to, any opinions or views with respect to the price or market for the Public SecuritiesUnits, do not constitute advice or recommendations to the CompanyPartnership Entities or the Selling Unitholder. The Company Each Partnership Entity and the Selling Unitholder hereby waives and releases, to the fullest extent permitted by law, any claims that the Company it may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company Partnership Entities or the Selling Unitholder in connection with the transactions contemplated by this Agreement or any matters leading up relating to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor.

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. October __, 2013 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCQUARTET MERGER CORP. By: Name: Xxxx X. Xxxxxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 20202013] SCHEDULE A PETRA ACQUISITION, INCQUARTET MERGER CORP. 7,500,000 Firm 8,400,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 8,400,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionQuartet Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Xxxx X. Xxxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Quartet Merger Corp. (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000$ , for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionQuartet Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Xxxx X. Xxxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Quartet Merger Corp. (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000$ , for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters underwriters, and the QIU is acting solely as a “qualified independent underwriter” within the meaning of FINRA Rule 5121, in connection with the offering of the Public SecuritiesOffering. The Company further acknowledges that the Underwriters and the QIU are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters or the QIU act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters or the QIU may undertake or have undertaken in furtherance of the offering of the Public SecuritiesOffering, either before or after the date hereof. The Underwriters and the QIU hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company Company, the Underwriters and the Underwriters QIU agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters or the QIU to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters or the QIU with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between among the Underwriters Underwriters, the QIU and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yourstruly yours, PETRA ACQUISITIONMONTEREY BIO ACQUISITION CORPORATION By: Name: Sxxxxxx Xxxxxx Title: Chief Executive Officer Agreed to and accepted on the date first above written. CHARDAN CAPITAL MARKETS, INC. LLC, as Representative of the several Underwriters By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor:

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. _________ __, 2014 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONCB PHARMA ACQUISITION CORP. By: Name: Lxxxxxx X. Xxxxxxxxx, M.D. Title: Chief Executive Officer Agreed to and accepted as of the date first written above: EARLYBIRDCAPITAL, INC. ., as Representative of the several Underwriters By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCCB PHARMA ACQUISITION CORP. 7,500,000 Firm 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. Aegis Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Corp. I-Banker Securities, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 4,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionCB Pharma Acquisition Corp. 20 Xxx Xxxxxxx Xxxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Lxxxxxx X. Xxxxxxxxx, M.D. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CB Pharma Acquisition Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,900,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionCB Pharma Acquisition Corp. 20 Xxx Xxxxxxx Xxxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Lxxxxxx X. Xxxxxxxxx, M.D. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CB Pharma Acquisition Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,900,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCACCRETION ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. SXXXXXXX INC. ., as Representative of the several Underwriters By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]______, 20202021] SCHEDULE A PETRA ACQUISITION, INCACCRETION ACQUISITION CORP. 7,500,000 Firm 15,00,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 Sxxxxxxx Inc. TOTAL 7,500,000 15,000,000 SCHEDULE B None. [to be finalized] EXHIBIT A Form of Target Business Letter Petra AcquisitionAccretion Acquisition Corp. 400 00xx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx#0000 Xxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Accretion Acquisition Corp. (the “Company”), dated [____]____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000151,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionAccretion Acquisition Corp. 400 00xx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx#0000 Xxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Accretion Acquisition Corp. (the “Company”), dated [____]____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000151,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company Issuers hereby acknowledges acknowledge that the Underwriters are acting solely as underwriters in connection with the offering purchase and sale of the Public SecuritiesNotes. The Company Issuers further acknowledges acknowledge that each of the Underwriters are is acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters any Underwriter act or be responsible as a fiduciary to the CompanyIssuers, its their management, stockholders, creditors or any other person in connection with any activity that the Underwriters such Underwriter may undertake or have has undertaken in furtherance of the offering purchase and sale of the Public SecuritiesNotes, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the CompanyIssuers, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company Issuers hereby confirms its confirm their understanding and agreement to that effect. The Company Issuers and the Underwriters each Underwriter agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters any Underwriter to the Company Issuers regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesNotes, do not constitute advice or recommendations to the CompanyIssuers. The Company Issuers hereby waives waive and releasesrelease, to the fullest extent permitted by law, any claims that the Company Issuers may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company Issuers in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing Underwriting Agreement correctly sets forth the understanding between among the Underwriters Issuers and the CompanyUnderwriters, please so indicate in the space provided below for that the purpose, whereupon this letter and your acceptance shall constitute a binding agreement between usamong the Issuers and the Underwriters. Very Truly Yours, PETRA ACQUISITIONBEAZER HOMES USA, INC. By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Agreed to Executive Vice President and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. Chief Financial Officer APRIL CORPORATION BEAZER ALLIED COMPANIES HOLDINGS, INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLCBEAZER GENERAL SERVICES, INC. By: Name: Title: By LADENBURG XXXXXXXX & COBEAZER HOMES CORP. BEAZER HOMES HOLDINGS CORP. BEAZER HOMES INDIANA HOLDINGS CORP. BEAZER HOMES SALES, INC. BEAZER HOMES TEXAS HOLDINGS, INC. BEAZER REALTY CORP. BEAZER REALTY, INC. BEAZER REALTY LOS ANGELES, INC. BEAZER REALTY SACRAMENTO, INC. BEAZER/XXXXXXX REALTY, INC. HOMEBUILDERS TITLE SERVICES OF VIRGINIA, INC. HOMEBUILDERS TITLE SERVICES, INC. By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [Signature Page to Underwriting AgreementSIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] BEAZER MORTGAGE CORPORATION By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: President BEAZER HOMES INDIANA LLP By: BEAZER HOMES INVESTMENTS, dated August LLC, its Managing Partner By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President XXXXX XXXX VENTURES, LLC BEAZER CLARKSBURG, LLC BEAZER COMMERCIAL HOLDINGS, LLC DOVE BARRINGTON DEVELOPMENT LLC BEAZER HOMES INVESTMENTS, LLC BEAZER HOMES MICHIGAN, LLC ELYSIAN HEIGHTS POTOMIA, LLC By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [__]SIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] BEAZER HOMES TEXAS, 2020] SCHEDULE A PETRA ACQUISITIONL.P. By: BEAZER HOMES TEXAS HOLDINGS, INC., its General Partner By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President BEAZER REALTY SERVICES, LLC By: BEAZER HOMES INVESTMENTS, LLC, its Sole Member By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President BEAZER SPE, LLC By: BEAZER HOMES HOLDINGS CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [SIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] BH BUILDING PRODUCTS, LP By: BH PROCUREMENT SERVICES, LLC, its General Partner By: BEAZER HOMES TEXAS, L.P., its Sole Member By: BEAZER HOMES TEXAS HOLDINGS, INC., its General Partner By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President BH PROCUREMENT SERVICES, LLC By: BEAZER HOMES TEXAS, L.P., its Sole Member By: BEAZER HOMES TEXAS HOLDINGS, INC., its General Partner By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [SIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] PARAGON TITLE, LLC By: BEAZER HOMES INVESTMENTS, LLC, its Sole Member and Manager By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President TRINITY HOMES, LLC By: BEAZER HOMES INVESTMENTS, LLC, its Member By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [SIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] CLARKSBURG ARORA LLC By: BEAZER CLARKSBURG, LLC, its Sole Member By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President CLARKSBURG SKYLARK, LLC By: CLARKSBURG ARORA LLC, its Sole Member By: BEAZER CLARKSBURG, LLC, its Sole Member By: BEAZER HOMES CORP., its Sole Member By: /s/ Xxxxx X. Xxxxxxx Name: Xxxxx X. Xxxxxxx Title: Executive Vice President [SIGNATURE PAGE TO SENIOR NOTES OFFERING UNDERWRITING AGREEMENT] Confirmed and accepted as of the date first above written: CREDIT SUISSE SECURITIES (USA) LLC as Representative of the Underwriters By: /s/ Xxxx Xxxxxxxx Name: Xxxx Xxxxxxxx Title: Managing Director CITIGROUP GLOBAL MARKETS INC. 7,500,000 Firm Units as Representative of the Underwriters By: /s/ Xxxxx Xxxxxx Name: Xxxxx Xxxxxx Title: Director Schedule I Underwriter Number Principal Amount of Firm Units to be Notes To Be Purchased LifeSci Capital Credit Suisse Securities (USA) LLC 5,000,000 Ladenburg Xxxxxxxx $120,000,000 Citigroup Global Markets Inc. $120,000,000 Deutsche Bank Securities Inc. $45,000,000 Moelis & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionCompany LLC $15,000,000 Total $300,000,000 Schedule II Guarantors Beazer General Services, Inc. 0 Beazer Homes Corp. Beazer/Xxxxxxx Realty, Inc. Beazer Homes Sales, Inc. Beazer Homes Investments, LLC Beazer Realty Corp. Beazer Homes Holdings Corp. Beazer Homes Indiana Holdings Corp. Beazer Homes Texas Holdings, Inc. Beazer Homes Texas, X.X. Xxxxxx Homes Indiana LLP April Corporation Beazer SPE, LLC Beazer Realty, Inc. Beazer Realty Services, LLC Beazer Realty Los Angeles, Inc. Beazer Realty Sacramento, Inc. BH Building Products, LP BH Procurement Services, LLC Homebuilders Title Services of Virginia, Inc. Homebuilders Title Services, Inc. Beazer Allied Companies Holdings, Inc. Paragon Title, LLC Trinity Homes, LLC Beazer Commercial Holdings, LLC Beazer Clarksburg, LLC Xxxxx Xxxx 00xx Ventures, LLC Beazer Mortgage Corporation Beazer Homes Michigan, LLC Dove Barrington Development LLC Clarksburg Arora LLC Clarksburg Skylark, LLC Elysian Heights Potomia, LLC Schedule III Subsidiary Jurisdiction of Incorporation or Formation Owners % Owned by the Company (directly or indirectly) Beazer Homes Corp. TN Beazer Homes Holdings Corp. 100 Beazer/Xxxxxxx Realty, Inc. NC Beazer Homes Corp. 100 Beazer Homes Sales, Inc. DE Beazer Homes Holdings Corp. 100 Beazer Realty Corp. GA Beazer Homes Corp. 100 Beazer Mortgage Corporation DE Beazer Homes USA, Inc. 100 Beazer General Services, Inc. DE Beazer Homes Holdings Corp. 100 Beazer Homes Holdings Corp. DE Beazer Homes USA, Inc. 100 Beazer Homes Texas Holdings, Inc. DE Beazer Homes Holdings Corp. 100 Beazer Homes Texas, X.X. XX Xxxxxx Xxx XxxxHomes Holdings Corp.; Beazer Homes Texas Holdings, Inc. 100 April Corporation CO Beazer Homes Holdings Corp. 100 Beazer SPE, LLC GA Beazer Homes Holdings Corp. 100 Beazer Homes Investments, LLC DE Beazer Homes Corp. 100 Beazer Realty, Inc. NJ Beazer Homes Corp. 100 Homebuilders Title Services of Virginia, Inc. VA Beazer Homes USA, Inc. 100 Homebuilders Title Services, Inc. DE Beazer Homes USA, Inc. 100 Beazer Allied Companies Holdings, Inc. DE Beazer Homes Holdings Corp. 100 United Home Insurance Company A Risk Retention Group VT Beazer Homes Corp.; Beazer Homes Holdings Corp.; Beazer Homes Texas Holdings, Inc. 100 Security Title Insurance Company VT Beazer Homes USA, Inc 100 Builders Homesite, Inc. DE Beazer Homes Holdings Corp. (Cooperative Consortium Among Builders) (Common 2,206,230 shares; Series A-2 Preferred 1,691,410) Paragon Title, LLC IN Beazer Homes Investments, LLC 100 Subsidiary Jurisdiction of Incorporation or Formation Owners % Owned by the Company (directly or indirectly) Trinity Homes, LLC IN Beazer Homes Investments, LLC; Beazer Homes Indiana LLP 100 Beazer Homes Indiana LLP IN Beazer Homes Investments, LLC; Beazer Homes Indiana Holdings Corp.; Beazer Homes Corp. 100 Beazer Homes Indiana Holdings Corp. DE Beazer Homes Investments, LLC 100 Beazer Realty Services, LLC DE Beazer Homes Investments, LLC 100 Beazer Realty Los Angeles, Inc. DE Beazer Homes Holdings Corp. 100 Beazer Realty Sacramento, Inc. DE Beazer Homes Holdings Corp. 100 BH Building Products, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionXX Xxxxxx Homes Texas, L.P.; BH Procurement Services, LLC 100 BH Procurement Services, LLC DE Beazer Homes Texas, L.P. 100 Beazer Commercial Holdings, LLC DE Beazer Homes Corp. 100 Beazer Clarksburg, LLC MD Beazer Homes Corp. 000 Xxxxx Xxxx Ventures, LLC FL Beazer Homes Corp. 100 Beazer Homes Capital Trust I DE Beazer Homes USA, Inc. (“Company”)* Beazer Homes Michigan, dated [____]LLC DE Beazer Homes Corp. 000 Xxxx Xxxxxxxxxx Development LLC DE Beazer Homes Corp. 100 Xxxxxxx Development LLC DE Beazer Homes Corp.; Centex Homes 99 Clarksburg Arora LLC MD Beazer Clarksburg, 2020 (LLC 100 Clarksburg Skylark, LLC MD Clarksburg Arora LLC 100 Elysian Heights Potomia, LLC VA Beazer Homes Corp. 100 * Statutory trust of which Beazer Homes USA, Inc. is the “Prospectus”)beneficiary. Capitalized terms used and However, Beazer Homes USA, Inc. does not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that exercise any control over Beazer Homes Capital Trust I. Schedule IV Subsidiary Jurisdiction of Incorporation or Formation Owners % Owned by the Company has established the Trust Account(directly or indirectly) Imagine Built Homes, initially in an amount Ltd TX Beazers Homes Texas, L.P.; B.F. Managing Partners, LLC; BFF Partners LTD 33.33 Castle Star Development Company, LLC CO April Corporation; Xxx Xxxx Building Corporation; North 180, LLC 49 Castle Star Commercial Investments, LLC CO April Corporation; Tadaptanam, LLC; Xxxxxxx X. Xxxxxxx; Xxxxx X. Xxxxxx 49 FallBrook Partners, LLC CO Beazer Homes Holdings Corp.; Meritage Homes of at least $75,750,000Colorado, for the benefit Inc. 00 Xxxxx Xxxxxxxxx Venture, LLC FL Beazer Homes Corp; Intervest Construction of the Public Stockholders and thatJAX, except for the interest earned on the amounts held in the Trust AccountInc. 50 West Xxxxxx, LLC FL Beazer Homes Corp; Intervest Construction of JAX, Inc. 50 South Edge, LLC NV Beazer Homes Holdings Corp; Focus South Group, LLC; MTH Homes Nevada, Inc.; Xxxxxx Investments, LLC; Xxxxxxx Xxxx Homes Nevada; Xxxxxx Homes of Nevada; Xxxxxxx-Toll Limited Partnership, LLC; Beazer Homes Holdings Corp.; KB Home Nevada Inc. 2.58 904 Georgetown Treatment Plant, LLC NC Beazer Homes Corp; North Star Management, Inc. Sandpiper Bay Land Company, Inc. 25 Belmont, LLC FL Beazer Homes Corp; Residential Funding Corporation 50 Long Lake Ranch, LLC FL Beazer Homes Corp; M/I Homes of Tampa, LLC 50 WCD Associates, LLC IN Beazer Homes Corp; MGB; Xxxx Xxxxx 37.5 Subsidiary Jurisdiction of Incorporation or Formation Owners % Owned by the Company may disburse monies from the Trust Account only: (idirectly or indirectly) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityFair Chase Development, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time periodLLC DE Beazer Homes Corp; Centex Homes 00 Xxxxxxxxx Xxxx Center, or (iii) to the Company concurrently withLLC VA Beazer Homes Corp.; Centex Homes; Van Metre Lansdowne Town Center, or after it consummatesLLC 50 Creekside Development, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with itLLC VA Beazer Homes Corp.; Centex Homes; Van Metre Creekside Investment, the undersigned hereby agrees that it does not have any rightLLC 49 Lansdowne Community Development, titleLLC VA Beazer Homes Corp.; Centex Homes; WL Homes LLC, interest or claim of any kind in or to any monies in the Trust Account (eachdba Xxxx Xxxxx homes; Van Metre Lansdowne Investments, a “Claim”) and hereby waives any Claim it may have in the future as a result ofLLC 25 Schedule V Pricing Term Sheet US$300,000,000 Beazer Homes USA, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorInc.

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCROC ENERGY ACQUISITION CORP. By: /s/ Xxxxxx Xxxxxxx Xxxxx Name: Xxxxxx Xxxxxxx Xxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]December 1, 20202021] SCHEDULE A PETRA ACQUISITION, INCROC ENERGY ACQUISITION CORP. 7,500,000 Firm 18,00,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. 17,800,000 Revere Securities LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 200,000 TOTAL 7,500,000 18,000,000 SCHEDULE B None. None EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx ROC Energy Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. ROC Energy Acquisition Corp. (the “Company”), dated [____]December 1, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000181,800,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx ROC Energy Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. ROC Energy Acquisition Corp. (the “Company”), dated [____]December 1, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000181,800,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. September 14, 2017 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA XXXXXX OAKWOOD TECHNOLOGY ACQUISITION, INC. By: /s/ Xxxxx Xxxxxxx Name: Xxxxx Xxxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]September 14, 20202017] SCHEDULE A PETRA XXXXXX OAKWOOD TECHNOLOGY ACQUISITION, INC. 7,500,000 Firm 5,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 EarlyBirdCapital, Inc. 4,200,000 I-Bankers Securities, Inc. 400,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 400,000 TOTAL 7,500,000 5,000,000 SCHEDULE B None. Investor Presentation dated September 2017 EXHIBIT A Form of Target Business Letter Petra Xxxxxx Oakwood Technology Acquisition, Inc. 0 c/x Xxxxxx Oakwood Investments, LLC 00 Xxxx 00xx Xxxxxx 0xx Xxx. Xxx XxxxXxxxx, XX Xxxxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Xxxxxx Oakwood Technology Acquisition, Inc. (the “Company”), dated [____]September 14, 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Xxxxxx Oakwood Technology Acquisition, Inc. 0 c/x Xxxxxx Oakwood Investments, LLC 00 Xxxx 00xx Xxxxxx 0xx Xxx. Xxx XxxxXxxxx, XX Xxxxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Xxxxxx Oakwood Technology Acquisition, Inc. (the “Company”), dated [____]September 14, 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. [______ __], 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCSPRINGWATER SPECIAL SITUATIONS CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [______ __], 20202021] SCHEDULE A PETRA ACQUISITION, INCSPRINGWATER SPECIAL SITUATIONS CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. [__] JonesTrading Institutional Services LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. [____] EXHIBIT A Form of Target Business Letter Petra AcquisitionSpringwater Special Situations Corp. c/o Graubard Xxxxxx 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Springwater Special Situations Corp. (the “Company”), dated [______ __], 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionSpringwater Special Situations Corp. c/o Graubard Xxxxxx 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Springwater Special Situations Corp. (the “Company”), dated [______ __], 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] I-Bankers Securities, Inc. ________, 2023 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. DISTOKEN ACQUISITION CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. I-BANKERS SECURITIES, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm DISTOKEN ACQUISITION CORPORATION 6,000,000 Units Underwriter Underwriters Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. I-Bankers Securities, Inc. 2,500,000 TOTAL 7,500,000 6,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____]______, 2020 2023 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____], 2020 2023 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL2, INC. By: /s/ Dr. Avi X. Xxxx Name: Dr. Avi X. Xxxx Title: CEO, President, Executive Chairman of the Board, and Secretary Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] CEO SCHEDULE A PETRA ACQUISITIONGIGCAPITAL2, INC. 7,500,000 15,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. 7,200,000 Northland Securities, Inc. 7,410,000 Odeon Capital Group LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 390,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. Investor Presentation, May 2019 EXHIBIT A Form of Target Business Letter Petra AcquisitionGigCapital2, Inc. 0 0000 X. Xxxxxxxx Xx., Xxxxx 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionGigCapital2, Inc. (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionGigCapital2, Inc. 0 0000 X. Xxxxxxxx Xx., Xxxxx 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionGigCapital2, Inc. (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. [l], 2017 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCBISON CAPITAL ACQUISITION CORP. By: ________________________________________ Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: ________________________________________ Name: Title: [Signature Page to Underwriting Agreement, dated August [__l], 20202017] SCHEDULE A PETRA ACQUISITION, INCBISON CAPITAL ACQUISITION CORP. 7,500,000 Firm 5,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC EarlyBirdCapital, Inc. [l] [_____] [l] TOTAL 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. Investor Presentation Dated May 2017 EXHIBIT A Form of Target Business Letter Petra AcquisitionBison Capital Acquisition Corp. 609-610 21st Century Tower Xx. 00 Xxxxxxxxxxx Xxxx Xxxxxxxx Xxxxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxx 000000, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bison Capital Acquisition Corp. (the “Company”), dated [____l], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00051,250,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionBison Capital Acquisition Corp. 609-610 21st Century Tower Xx. 00 Xxxxxxxxxxx Xxxx Xxxxxxxx Xxxxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxx 000000, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bison Capital Acquisition Corp. (the “Company”), dated [____l], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00051,250,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. March 10, 2016 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCKLR ENERGY ACQUISITION CORP. By: /s/ Exxxxx Xxxxxxx Name: Exxxxx Xxxxxxx Title: President Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]March 10, 20202016] SCHEDULE A PETRA ACQUISITION, INCKLR ENERGY ACQUISITION CORP. 7,500,000 Firm 8,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. 7,200,000 Chardan Capital Markets, LLC 5,000,000 Ladenburg Xxxxxxxx & Co. 500,000 I-Bankers Securities, Inc. 2,500,000 300,000 TOTAL 7,500,000 SCHEDULE B None. 8,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionKLR Energy Acquisition Corp. 800 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx Xxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. KLR Energy Acquisition Corp. (the “Company”), dated [____]March 10, 2020 2016 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00083,200,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionKLR Energy Acquisition Corp. 800 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx Xxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. KLR Energy Acquisition Corp. (the “Company”), dated [____]March 10, 2020 2016 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00083,200,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. December 7, 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDD3 ACQUISITION CORP. II By: /s/ Mxxxxx Xxxxxx Name: Mxxxxx Xxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: CEO [Signature Page to Underwriting Agreement, dated August [__]December 7, 2020] SCHEDULE A PETRA ACQUISITION, INCDD3 ACQUISITION CORP. 7,500,000 Firm II 11,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 9,900,000 1,100,000 TOTAL 7,500,000 11,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionDD3 Acquisition Corp. II Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx, Xxxxxxxx 000 Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. II (the “Company”), dated [____]December 7, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000110,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDD3 Acquisition Corp. II Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx, Xxxxxxxx 000 Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. II (the “Company”), dated [____]December 7, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000110,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] Moelis & Company LLC Xxxxxxxxxxx & Co. Inc. __________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCCACTUS ACQUISITION CORP. 1 LIMITED By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL Moelis & Company LLC LADENBURG XXXXXXXX & CO. INC. For themselves and ., as Representatives Co-Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX Xxxxxxxxxxx & CO. INC. Co. Inc., as Co-Representative of the several Underwriters By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]________, 20202021] SCHEDULE A PETRA ACQUISITION, INCCACTUS ACQUISITION CORP. 7,500,000 Firm 1 LIMITED 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx Xxxxxxxxxxx & Co. Inc. 2,500,000 Moelis & Company LLC TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxCactus Acquisition Corp. 1 Limited 0X Xxxxx Xxxxx Xxxxx Xxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cactus Acquisition Corp. 1 Limited (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxCactus Acquisition Corp. 1 Limited 0X Xxxxx Xxxxx Xxxxx Xxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cactus Acquisition Corp. 1 Limited (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company and the Placement Investors hereby acknowledges acknowledge that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany's securities. The Company and the Placement Investors further acknowledges acknowledge that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, Company and its management, stockholders, creditors equity holders, creditors, the Placement Investors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany's securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company Company, the Placement Investors and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany's securities, do not constitute advice or recommendations to the CompanyCompany of the Placement Investors. The Company and the Placement Investors hereby waives waive and releasesrelease, to the fullest extent permitted by law, any claims that claim the Company or its Affiliates or the Placement Investors may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to involving such transactions. [Signature Page Follows] Maxim Group LLC _________________, 2007 Page 50 of 50 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. ALPHA SECURITY GROUP CORPORATION By: -------------------------------------- Name: Title: Agreed to and AcceptedAGREED TO AND ACCEPTED AS OF THE DATE FIRST WRITTEN ABOVE: LIFESCI CAPITAL MAXIM GROUP LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: -------------------------------------- Name: Xxxxxxxx X. Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. ByDirector of Investment Banking AGREED TO AND ACCEPTED AS TO THE COMPANY AND THE UNDERSIGNED, BUT SOLELY WITH RESPECT TO SECTIONS 1.4, 1.6 AND 10.6 HEREOF: Name------------------------------------------ Xxxxxx X. Xxxxxxxxx AGREED TO AND ACCEPTED AS TO THE COMPANY AND THE UNDERSIGNED, BUT SOLELY WITH RESPECT TO SECTIONS 1.4, 1.6 AND 10.6 HEREOF: Title: [Signature Page to Underwriting Agreement------------------------------------------ Xxxxxxxxxxxx Xxxxxxxx SCHEDULE A ALPHA SECURITY GROUP CORPORATION 6,000,000 UNITS NUMBER OF FIRM UNITS UNDERWRITER TO BE PURCHASED -------------------------------------------------------------------------------- Maxim Group LLC I-Bankers Securities, dated August [Inc. ------------------------ 6,000,000 EXHIBIT A FORM OF TARGET BUSINESS LETTER __]________________, 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 200___ Alpha Security Group Corporation 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Alpha Security Group Corporation (“Company”"ALPHA"), dated [____]________, 2020 2007 (the “Prospectus”"PROSPECTUS"). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have The authorized signatory of the undersigned business entity (collectively, with its officers, directors, employees, owners, affiliates, agents and representatives, "TARGET COMPANY") has read the Prospectus and understand understands that the Company Alpha has established a trust account (collectively with the Trust Accountinitial principal and interest accrued from time to time thereon, the "TRUST ACCOUNT"), initially in an amount of at least $75,750,00060,000,000 ($68,820,000 if the over-allotment option is exercised in full), for the benefit of Alpha's public stockholders and the Public Stockholders underwriters of Alpha's initial public offering and that, except for $1,825,000 ($1,925,000 if the over-allotment option is exercised in full) of the interest earned (after payment of applicable taxes) on the amounts held in the Trust Account, the Company Alpha may disburse monies from the Trust Account only: (i) to the Public Stockholders such public stockholders in the event of the conversion of their shares upon consummation or the dissolution and liquidation of a Business Combination Alpha or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation Alpha and such underwriters after Alpha consummates a business combination (as described in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business CombinationProspectus). For and in consideration of the Company Alpha agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, and for other good and valuable consideration, the undersigned receipt and sufficiency of which is hereby acknowledged, Target Company hereby agrees that it does not now and shall not at any time hereafter have any rightclaim to, titleor make any claim against, interest or claim of any kind in or to any monies in the Trust Account or Alpha's public stockholders, regardless of whether such claim arises as a result of, in connection with or relating in any way to, the business relationship between Alpha and Target Company, this waiver letter or any other matter, and regardless of whether such claim arises based on contract, tort, equity or any other theory of legal liability (each, a “Claim”) any and all such claims are collectively referred to hereafter as the "CLAIMS"). Target Company hereby irrevocably waives any Claim it may have have, now or in the future as a result offuture, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against against, the Trust Account or such public stockholders for any reason whatsoever. In the event that Target Company commences any action or proceeding based upon, in connection with, relating to or arising out of any matter relating to Alpha, which proceeding seeks, in whole or in part, relief against the Trust Account or Alpha's public stockholders, whether in the form of money damages or injunctive relief, in which Alpha or such beneficiaries prevail, whether on the merits or otherwise, then Alpha shall be entitled to recover from Target Company and/or the party(ies) who commenced the action or proceeding, the legal fees and associated costs required to defend such action or proceeding. ---------------------------------------- Print Name of Target Business Company ---------------------------------------- ---------------------------------------- Authorized Signature of Target Business Company EXHIBIT B Form of Vendor Letter Petra AcquisitionFORM OF VENDOR LETTER __________________, Inc. 0 200___ Alpha Security Group Corporation 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Alpha Security Group Corporation (“Company”"ALPHA"), dated [____]________, 2020 2007 (the “Prospectus”"PROSPECTUS"). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have The authorized signatory of the undersigned vendor and/or service provider of Alpha (collectively, with its officers, directors, employees, owners, affiliates, agents and representatives, "VENDOR") has read the Prospectus and understand understands that the Company Alpha has established a trust account (collectively with the Trust Accountinitial principal and interest accrued from time to time thereon, the "TRUST ACCOUNT"), initially in an amount of at least $75,750,00060,000,000 ($68,820,000 if the over-allotment option is exercised in full), for the benefit of Alpha's public stockholders and the Public Stockholders underwriters of Alpha's initial public offering and that, except for $1,825,000 ($1,925,000 if the over-allotment option is exercised in full) of the interest earned (after payment of applicable taxes) on the amounts held in the Trust Account, the Company Alpha may disburse monies from the Trust Account only: (i) to the Public Stockholders such public stockholders in the event of the conversion of their shares upon consummation or the dissolution and liquidation of a Business Combination Alpha or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation Alpha and such underwriters after Alpha consummates a business combination (as described in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business CombinationProspectus). For and in consideration of the Company Alpha agreeing to use the retain Vendor to provide goods or services of the undersignedto Alpha, and for other good and valuable consideration, the undersigned receipt and sufficiency of which is hereby acknowledged, Vendor hereby agrees that it Vendor does not now and shall not at any time hereafter have any rightclaim to, titleor make any claim against, interest or claim of any kind in or to any monies in the Trust Account or Alpha's public stockholders, regardless of whether such claim arises as a result of, in connection with or relating in any way to, the business relationship between Alpha and Vendor, this waiver letter or any other matter, and regardless of whether such claim arises based on contract, tort, equity or any other theory of legal liability (each, a “Claim”) any and all such claims are collectively referred to hereafter as the "CLAIMS"). Vendor hereby irrevocably waives any Claim it may have have, now or in the future as a result offuture, or arising out of, any services provided to the Company and will not seek recourse against against, the Trust Account or such public stockholders for any reason whatsoever. In the event that Vendor commences any action or proceeding based upon, in connection with, relating to or arising out of any matter relating to Alpha, which proceeding seeks, in whole or in part, relief against the Trust Account or Alpha's public stockholders, whether in the form of money damages or injunctive relief, in which Alpha or such beneficiaries prevail, whether on the merits or otherwise, then Alpha shall be entitled to recover from Vendor and/or the party(ies) who commenced the action or proceeding, the legal fees and associated costs required to defend such action or proceeding. ---------------------------------------- Print Name of Vendor Authorized Signature of Vendor----------------------------------------

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. ___________, 2022 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. II By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_________, 20202022] SCHEDULE A PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. 7,500,000 Firm II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000102,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000102,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. _________ __, 2014 Page 42 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC1347 CAPITAL CORP. By: Name: Gxxxxx Xxxxx Title: President and Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 20202014] SCHEDULE A PETRA ACQUISITION, INC1347 CAPITAL CORP. 7,500,000 Firm 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 4,000,000 EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx 1347 Capital Corp. 100 Xxxxxx Xxx Xxxx, XX 00000 6th Floor Itasca, IL 60143 Attn: Xxxxxxx Xxxxxxxx Gxxxxx Xxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. 1347 Capital Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx 1347 Capital Corp. 100 Xxxxxx Xxx Xxxx, XX 00000 6th Floor Itasca, IL 60143 Attn: Xxxxxxx Xxxxxxxx Gxxxxx Xxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. 1347 Capital Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCMERIDA MERGER CORP. I By: /s/ Xxxxx Xxx Name: Xxxxx Xxx Title: President Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]November 4, 20202019] SCHEDULE A PETRA ACQUISITION, INCMERIDA MERGER CORP. 7,500,000 I 12,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 EarlyBirdCapital, Inc. 9,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 3,000,000 TOTAL 7,500,000 SCHEDULE B None. 12,000,000 Schedule X-0 XXXXXXXX X Xxxx EXHIBIT A Form of Target Business Letter Petra AcquisitionMerida Merger Corp. I 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Merida Merger Corp. I (“Company”), dated [____]November 4, 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000120,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionMerida Merger Corp. I 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Merida Merger Corp. I (“Company”), dated [____]November 4, 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000120,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and Company, the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDIGITAL HEALTH ACQUISITION CORP. By: /s/ Sxxxx Xxxx Name: Sxxxx Xxxx Title: Chief Executive Officer Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and accepted as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendordate first written above:

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany's securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany's securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany's securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. Broadband Capital Management LLC March [ ], 2008 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCXXXXXXXXX ASIA ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI BROADBAND CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and MANAGEMENT LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: T. Xxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Managing Director [Signature Page to Underwriting Agreement, dated August [__]_________________, 20202008] SCHEDULE A PETRA ACQUISITION, INCXXXXXXXXX ASIA ACQUISITION CORP. 7,500,000 Firm 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Broadband Capital Management LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. Chardan Capital Markets, LLC 4,000,000 EXHIBIT A FORM OF LOEB & LOEB LLP OPINION EXHIBIT B FORM OF XXXXXXX, XXXX & XXXXXXX OPINION EXHIBIT C Form of Target Business Letter Petra AcquisitionXxxxxxxxx Asia Acquisition Corp. 00/X Xxxxx 0, Inc. 0 Xxx Xxxxx Xxxxx 00 Xxxxxx Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and GentlemenXxxx Xxxx Xxxxxxxxx: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Xxxxxxxxx Asia Acquisition Corp. (the “Company”), dated [____]___________, 2020 2008 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, 31,680,000 for the benefit of the Public Stockholders Shareholders and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; or (ii) to the Public Stockholders in connection with Company and the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or Underwriters after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B D Form of Vendor Letter Petra AcquisitionXxxxxxxxx Asia Acquisition Corp. 00/X Xxxxx 0, Inc. 0 Xxx Xxxxx Xxxxx 00 Xxxxxx Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and GentlemenXxxx Xxxx Xxxxxxxxx: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Xxxxxxxxx Asia Acquisition Corp. (the “Company”), dated [____]___________, 2020 2008 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, 31,680,000 for the benefit of the Public Stockholders Shareholders and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the interest earned on the amounts held in the Trust AccountAccount (which interest may, prior to the consummation of a business combination or the Company’s liquidation, be released (i) to the Company to pay taxes it has incurred, (ii) to redeeming shareholders voting against the extended period, as described in the Prospectus and (iii) to the Company, from time to time, to fund its working capital and general corporate requirements), the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; or (ii) to the Public Stockholders in connection with Company and the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or Underwriters after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters underwriters, and the QIU is acting solely as a “qualified independent underwriter” within the meaning of FINRA Rule 5121, in connection with the offering of the Public SecuritiesOffering. The Company further acknowledges that the Underwriters and the QIU are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters or the QIU act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters or the QIU may undertake or have undertaken in furtherance of the offering of the Public SecuritiesOffering, either before or after the date hereof. The Underwriters and the QIU hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company Company, the Underwriters, and the Underwriters QIU agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters or the QIU to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters or the QIU with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters Underwriters, the QIU and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yourstruly yours, PETRA ACQUISITION, INCMANA CAPITAL ACQUISITION CORP. By: /s/ Xxxxxxxx Xxxxxxxx Name: Xxxxxxxx Xxxxxxxx Title: Chief Executive Officer Agreed to and Accepted: LIFESCI CAPITAL LLC accepted on the date first above written. LADENBURG XXXXXXXX & CO. INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxx Xxxxxx Name: Xxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. Head of Capital Markets I-BANKERS SECURITIES, INC. ., as Qualified Independent Underwriter By: /s/ Xxxxxxx Xxxxxxx Name: Xxxxxxx Xxxxxxx Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] President SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm MANA CAPITAL ACQUISITION CORP 6,200,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 5,580,000 I-Bankers Securities, Inc. 620,000 TOTAL 7,500,000 SCHEDULE B None6,200,000 Sales Concession $ 0.12 Management $ 0.04 Underwriting $ 0.04 TOTAL $ 0.20 Sch. A EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Mana Capital Acquisition Corp. Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Mana Capital Acquisition Corp. (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Accounta “trust account”, initially in an amount of at least $75,750,000, 62,000,000 for the benefit of the Public Stockholders “public stockholders” and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the (i) interest earned on the amounts held trust account that may be released to the Company to pay any taxes it incurs, and (ii) interest earned by the trust account that may be released to the Company from time to time to fund the Company’s working capital and general corporate requirements, proceeds in the Trust Account, the Company may disburse monies from the Trust Account only: trust account will not be released (a) until (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination Combination, or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s dissolution and liquidation in the event of the Company if it is unable to consummate a Business Combination within the required allotted time period, or (iiib) to the Company concurrently with, public stockholders in the event they elect to redeem their shares of Common Stock in connection with a stockholder vote to approve an amendment to the Company’s amended and restated certificate of incorporation (A) to modify the substance or after it consummates, a Business Combinationtiming of the Company’s obligation to allow redemption rights as described in the Prospectus or (B) with respect to any other provision relating to stockholders’ rights or pre-initial business combination activity. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination business combination or other form of acquisition with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account trust account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business Ex. A EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Mana Capital Acquisition Corp. Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Mana Capital Acquisition Corp. (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Accounta “trust account”, initially in an amount of at least $75,750,000, 62,000,000 for the benefit of the Public Stockholders “public stockholders” and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the (i) interest earned on the amounts held trust account that may be released to the Company to pay any taxes it incurs, and (ii) interest earned by the trust account that may be released to the Company from time to time to fund the Company’s working capital and general corporate requirements, proceeds in the Trust Account, trust account will not be released (a) until(i) the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination Combination, or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s dissolution and liquidation in the event of the Company if it is unable to consummate a Business Combination within the required time periodallotted time, or (iiib) to the Company concurrently with, public stockholders in the event they elect to redeem their shares of Common Stock in connection with a stockholder vote to approve an amendment to the Company’s amended and restated certificate of incorporation (A) to modify the substance or after it consummates a Business Combinationtiming of the Company’s obligation to allow redemption rights as described in the Prospectus or (B) with respect to any other provision relating to stockholders’ rights or pre-initial business combination activity. For and in consideration of the Company agreeing to use the products or services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account trust account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc.[l], 2017Page 41 of 41 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. CM SEVEN STAR ACQUISITION CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm CM SEVEN STAR ACQUISITION CORPORATION 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 [l] [_____] [l] TOTAL 7,500,000 SCHEDULE B None. 15,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionCM Seven Star Acquisition Corporation Suite 1003-1004, Inc. 0 Xxxx 00xx 00/X, XXXX Xxxxx Xxxxx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxxx, Xxxx Xxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CM Seven Star Acquisition Corporation (the “Company”), dated [____l], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionCM Seven Star Acquisition Corporation Suite 1003-1004, Inc. 0 Xxxx 00xx 00/X, XXXX Xxxxx Xxxxx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxxx, Xxxx Xxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CM Seven Star Acquisition Corporation (the “Company”), dated [____l], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company Issuers and the Guarantors hereby acknowledges acknowledge that the Underwriters are each Initial Purchaser is acting solely as underwriters initial purchaser in connection with the offering purchase and sale of the Public Stage I Securities. The Company Issuers and the Guarantors further acknowledges acknowledge that the Underwriters are each Initial Purchaser is acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis basis, and in no event do the parties intend that the Underwriters Initial Purchasers act or be responsible as a fiduciary to either the CompanyIssuers, its the Guarantors or their respective management, stockholders, stockholders or creditors or any other person in connection with any activity that the Underwriters Initial Purchasers may undertake or have undertaken in furtherance of the offering purchase and sale of the Public Stage I Securities, either before or after the date hereof. The Underwriters Initial Purchasers hereby expressly disclaim any fiduciary or similar obligations to either the CompanyIssuers or the Guarantors, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company Issuers and the Guarantors hereby confirms its confirm their understanding and agreement to that effect. The Company Issuers, the Guarantors and the Underwriters Initial Purchasers agree that they are each responsible for making their own independent judgments with respect to any such transactions, transactions and that any opinions or views expressed by the Underwriters Initial Purchasers to the Company Issuers and the Guarantors regarding such transactions, including including, but not limited to to, any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the CompanyIssuers and the Guarantors. The Company Issuers and the Guarantors hereby waives waive and releasesrelease, to the fullest extent permitted by law, any claims that either the Company Issuers or the Guarantors may have against the Underwriters Initial Purchasers with respect to any breach or alleged breach of any fiduciary or similar duty to the Company Issuers or the Guarantors in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor.

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. _____________, 2013 Page 40 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCMEDWORTH ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]__________, 20202013] SCHEDULE A PETRA ACQUISITION, INCMEDWORTH ACQUISITION CORP. 7,500,000 Firm Units 6,000,000 Shares of Common Stock Underwriter Number of Firm Units Shares to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 6,000,000 EXHIBIT A Form of Legal Opinion EXHIBIT B Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx MedWorth Acquisition Corp. 000 Xxxxxxxx Xxxxxx Xxx XxxxXxxxx 000 Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and X. Xxxxxx Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. MedWorth Acquisition Corp. (the “Company”), dated [____]__ __, 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,160,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityCombination, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B C Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx MedWorth Acquisition Corp. 000 Xxxxxxxx Xxxxxx Xxx XxxxXxxxx 000 Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and X. Xxxxxx Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. MedWorth Acquisition Corp. (the “Company”), dated [____]__ __, 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,160,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityCombination, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany’s securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. 44 Maxim Group LLC September 24, 2007 Page 45 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCSEANERGY MARITIME CORP. By: /s/ Panagiotis Zafet Name: Panagiotis Zafet Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and MAXIM GROUP LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Cxxxxxxx X. Xxxxxx Name: Cxxxxxxx X. Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Director of Investment Banking [Signature Page to Underwriting Agreement, dated August [__]September 24, 20202007] 45 SCHEDULE A PETRA ACQUISITION, INCSEANERGY MARITIME CORP. 7,500,000 Firm 22,000,000 Units Underwriter Number of Firm Units Underwriter to be Purchased LifeSci Maxim Group LLC 15,000,000 Ramius Securities, L.L.C. 4,500,000 I-Bankers Securities, Inc. 700,000 Rxxx Capital Partners, LLC 5,000,000 Ladenburg Xxxxxxxx 700,000 Broadband Capital Management, LLC 550,000 Pali Capital, Inc. 260,000 Legend Merchant Group, Inc. 170,000 Charden Capital Merkets, LLC 100,000 Jesup & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. Lxxxx Securities Corporation 20,000 22,000,000 EXHIBIT A Form FORM OF LOEB & LOEB OPINION 300 Xxxx Xxxxxx Direct 212.407.4000 Nxx Xxxx, XX 00000-0000 Main 212.407.4000 Fax 200.000.0000 September 28, 2007 Maxim Group LLC as representative of Target Business Letter Petra Acquisitionseveral underwriters 400 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx 0xx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made We have acted as counsel to Seanergy Maritime Corp., a Mxxxxxxx Islands corporation (the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 in connection with (a) the public offering (the “ProspectusIPO”) being underwritten by you and the other Underwriters of 23,100,000 Units (“Units”), each Unit consisting of one share of the Company’s common stock, par value $.0001 per share (the “Common Stock”), and one warrant to purchase one share of Common Stock (the “Warrants”), which includes 1,100,000 Units (the “Over-Allotment Units”) for which the Underwriters have exercised their over-allotment option (including all shares of Common Stock issued or issuable on exercise of Warrants issued as part of the Units and Over-Allotment Units and the Warrants so issued), pursuant to that certain Underwriting Agreement by and among the Company, the Representative and the other Underwriters party thereto, dated September 24, 2007 (the “Underwriting Agreement”); and (b) the Private Placement (“Private Placement”) of 16,016,667 Warrants pursuant to a certain Amended and Restated Subscription Agreement between the Company and each of its executive officers (“Subscription Agreement”). Capitalized This opinion is being delivered to you pursuant to Section 4.2.1 of the Underwriting Agreement. All capitalized terms used and herein, but not otherwise defined herein herein, shall have the respective meanings assigned to given them in the ProspectusUnderwriting Agreement. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in In connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time periodrendering of our opinion, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendorwe have:

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. _________ __, 2014 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONCB PHARMA ACQUISITION CORP. By: Name: Lxxxxxx X. Xxxxxxxxx, M.D. Title: Chief Executive Officer Agreed to and accepted as of the date first written above: EARLYBIRDCAPITAL, INC. ., as Representative of the several Underwriters By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCCB PHARMA ACQUISITION CORP. 7,500,000 Firm 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 4,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionCB Pharma Acquisition Corp. 20 Xxx Xxxxxxx Xxxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Lxxxxxx X. Xxxxxxxxx, M.D. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CB Pharma Acquisition Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionCB Pharma Acquisition Corp. 20 Xxx Xxxxxxx Xxxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Lxxxxxx X. Xxxxxxxxx, M.D. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. CB Pharma Acquisition Corp. (the “Company”), dated [____], 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. June 14, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDILA CAPITAL ACQUISITION CORP. By: /s/ Jxxxx Xxxxx Name: Jxxxx Xxxxx Title: Chief Financial Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] CEO SCHEDULE A PETRA ACQUISITION, INCDILA CAPITAL ACQUISITION CORP. 7,500,000 Firm 5,500,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 5,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionDILA Capital Acquisition Corp. 1000 Xxxxxxxx Xxx., Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxx. 000 Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DILA Capital Acquisition Corp. (the “Company”), dated [____]June 14, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00055,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDILA Capital Acquisition Corp. 1000 Xxxxxxxx Xxx., Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxx. 000 Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DILA Capital Acquisition Corp. (the “Company”), dated [____]June 14, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00055,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. [______], 2019 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCTUSCAN HOLDINGS CORP. By: Name: Xxxxxxx X. Xxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [______], 20202019] SCHEDULE A PETRA ACQUISITION, INCTUSCAN HOLDINGS CORP. 7,500,000 20,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 I-Bankers Securities, Inc. TOTAL 7,500,000 20,000,000 SCHEDULE B None. Investor Presentation dated [________] EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Tuscan Holdings Corp. 000 Xxxx 00xx Xxxxxx Xxxxxx, 00xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Tuscan Holdings Corp. (“Company”), dated [______], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000200,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Tuscan Holdings Corp. 000 Xxxx 00xx Xxxxxx Xxxxxx, 00xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Tuscan Holdings Corp. (“Company”), dated [______], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000200,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as the underwriters in connection with the offering purchase and sale of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, stockholders or creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering purchase and sale of the Public Securities, Company’s securities either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between among the Underwriters Company and the CompanyUnderwriters, please so indicate in the space provided below for that purpose, whereupon this letter Agreement and the Underwriter’s acceptance shall constitute a binding agreement between usamong the Company and the Underwriters. Very Truly Yourstruly yours, PETRA ACQUISITIONDHT HOLDINGS, INC. By: Name: Title: Agreed to Accepted and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For agreed as of the date first written above, on behalf of themselves and as Representatives of the several other Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. A: By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Name Title SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units LIST OF UNDERWRITERS Name of Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 shares of common stock Total...................................................................................... SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionPERMITTED FREE WRITING PROSPECTUSES [•] SCHEDULE C CERTAIN INFORMATION [•] SCHEDULE D SUBSIDIARIES AND VESSELS Subsidiary Vessel Owned DHT Maritime, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (inone) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to preAxx Tanker Corporation OverseasAnn Cxxxx Tanker Corporation OverseasChris Regal Unity Tanker Corporation OverseasRegal Cxxxx Tanker Corporation OverseasCathy Sophie Tanker Corporation OverseasSophie Rxxxxxx Tanker Corporation OverseasRebecca Ania Aframax Corporation OverseasAnia London Tanker Corporation OverseasLondon Newcastle Tanker Corporation OverseasNewcastle SCHEDULE E PERSONS REQUIRED TO DELIVER LOCK-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorUP AGREEMENTS

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters underwriters, and the QIU is acting solely as a “qualified independent underwriter” within the meaning of FINRA Rule 5121, in connection with the offering of the Public SecuritiesOffering. The Company further acknowledges that the Underwriters and the QIU are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters or the QIU act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters or the QIU may undertake or have undertaken in furtherance of the offering of the Public SecuritiesOffering, either before or after the date hereof. The Underwriters and the QIU hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company Company, the Underwriters and the Underwriters QIU agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters or the QIU to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters or the QIU with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between among the Underwriters Underwriters, the QIU and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yourstruly yours, PETRA ACQUISITION, INCCHARDAN NEXTECH ACQUISITION 2 CORP. By: /s/ Xxxxx Xxxxxxxx Name: Xxxxx Xxxxxxxx Title: Chief Executive Officer Agreed to and Accepted: LIFESCI accepted on the date first above written. CHARDAN CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and MARKETS, LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxx Xxxxxx Name: Xxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. Managing Partner X. XXXXX SECURITIES, INC. ., as Qualified Independent Underwriter By: /s/ Xxxxxxx XxXxxxxx Name: Xxxxxxx XxXxxxxx Title: Co-Head of Investment Banking [Signature Page to of the Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCCHARDAN NEXTECH ACQUISITION 2 CORP. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Chardan Capital Markets, LLC 5,000,000 Ladenburg Xxxxxxxx & Co. 10,950,000 X. Xxxxx Securities, Inc. 2,500,000 50,000 TOTAL 7,500,000 SCHEDULE B None. 11,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionChardan NexTech Acquisition 2 Corp. 00 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxx Xxxxxxxx, Chief Executive Officer Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Chardan NexTech Acquisition 2 Corp. (the “Company”), dated [____]August 10, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Accounta “trust account”, initially in an amount of at least $75,750,000, 111,650,000 for the benefit of the Public Stockholders “public stockholders” and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the interest earned on the amounts held trust account that may be released to the Company to pay any taxes it incurs, proceeds in the Trust Account, trust account will not be released until (a) the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination Combination, or amendment to (b) the Company’s Amended dissolution and Restated Certificate liquidation of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company if it is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combinationallotted time. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination business combination or other form of acquisition with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account trust account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionChardan NexTech Acquisition 2 Corp. 00 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxx Xxxxxxxx, Chief Executive Officer Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Chardan NexTech Acquisition 2 Corp. (the “Company”), dated [____]August 10, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Accounta “trust account”, initially in an amount of at least $75,750,000, 111,650,000 for the benefit of the Public Stockholders “public stockholders” and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for the interest earned on the amounts held trust account that may be released to the Company to pay any taxes it incurs, proceeds in the Trust Account, trust account will not be released until (a) the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination Combination, or amendment to (b) the Company’s Amended dissolution and Restated Certificate liquidation of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company if it is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combinationallotted time. For and in consideration of the Company agreeing to use the products or services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account trust account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCMERIDA MERGER CORP. I By: Name: Xxxxx Xxx Title: President Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__], 20202019] SCHEDULE A PETRA ACQUISITION, INCMERIDA MERGER CORP. 7,500,000 I 10,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg EarlyBirdCapital, Inc. [__] [__] [__] TOTAL 10,000,000 XXXXXXXX X Xxxx Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. X-0 EXHIBIT A Form of Target Business Letter Petra AcquisitionMerida Merger Corp. I 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Merida Merger Corp. I (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business Exh. A-1 EXHIBIT B Form of Vendor Letter Petra AcquisitionMerida Merger Corp. I 000 Xxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Merida Merger Corp. I (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCLEGATO MERGER CORP. By: Name: Xxxxx X. Xxxx Title: President Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCLEGATO MERGER CORP. 7,500,000 17,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg EarlyBirdCapital, Inc. [__] [__] [__] TOTAL 175,000,000 XXXXXXXX X Xxxx Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. X-0 EXHIBIT A Form of Target Business Letter Petra AcquisitionLegato Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Legato Merger Corp. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business Exh. A-1 EXHIBIT B Form of Vendor Letter Petra AcquisitionLegato Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Legato Merger Corp. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. ____________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCEUROPEAN SUSTAINABLE GROWTH ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_______, 20202021] SCHEDULE A PETRA ACQUISITION, INCEUROPEAN SUSTAINABLE GROWTH ACQUISITION CORP. 7,500,000 Firm 12,500,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 ABN AMRO Securities (USA) LLC. TOTAL 7,500,000 12,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 European Sustainable Growth Acquisition Corp. 00 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. European Sustainable Growth Acquisition Corp. (the “Company”), dated [____]_____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 European Sustainable Growth Acquisition Corp. 00 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. European Sustainable Growth Acquisition Corp. (the “Company”), dated [____]_____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. January 21, 2021 Page 39 of 39 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCEUROPEAN SUSTAINABLE GROWTH ACQUISITION CORP. By: /s/ Xxxxx Xxxxxx Name: Xxxxx Xxxxxx Title: President Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]January 21, 20202021] SCHEDULE A PETRA ACQUISITION, INCEUROPEAN SUSTAINABLE GROWTH ACQUISITION CORP. 7,500,000 Firm 12,500,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. 8,125,000 ABN AMRO Securities (USA) LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 4,375,000 TOTAL 7,500,000 12,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 European Sustainable Growth Acquisition Corp. 00 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. European Sustainable Growth Acquisition Corp. (the “Company”), dated [____]January 21, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 European Sustainable Growth Acquisition Corp. 00 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. European Sustainable Growth Acquisition Corp. (the “Company”), dated [____]January 21, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc.October 11, 2018Page 44 of 44 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDD3 ACQUISITION CORP. By: /s/ Mxxxxx Xxxxxx Name: Mxxxxx Xxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: CEO [Signature Page to Underwriting Agreement, dated August [__]October 11, 20202018] SCHEDULE A PETRA ACQUISITION, INCDD3 ACQUISITION CORP. 7,500,000 Firm 5,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC EarlyBirdCapital, Inc. 4,500,000 I-Bankers Securities, Inc. 500,000 TOTAL 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. Investor Presentation, September 2018 EXHIBIT A Form of Target Business Letter Petra AcquisitionDD3 Acquisition Corp. c/o DD3 Mex Acquisition Corp Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. (the “Company”), dated [____]October 11, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDD3 Acquisition Corp. c/o DD3 Mex Acquisition Corp Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. (the “Company”), dated [____]October 11, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCROC ENERGY ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_______, 20202021] SCHEDULE A PETRA ACQUISITION, INCROC ENERGY ACQUISITION CORP. 7,500,000 Firm 15,00,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. None EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx ROC Energy Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. ROC Energy Acquisition Corp. (the “Company”), dated [____]_____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000151,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx ROC Energy Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. ROC Energy Acquisition Corp. (the “Company”), dated [____]_____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000151,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc.December 19, 2022Page 37 of 37 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. ALPHAVEST ACQUISITION CORP By: /s/ Yxxx (Dxxxx) Yan Name: Yxxx (Dxxxx) Yan Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Mxxxxxx Xxxxxx Name: Mxxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Managing Director [Signature Page to Underwriting Agreement, dated August [__]December 19, 20202022] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm ALPHAVEST ACQUISITION CORP 6,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 5,100,000 Revere Securities 900,000 TOTAL 7,500,000 6,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx AlphaVest Acquisition Corp Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. AlphaVest Acquisition Corp. (the “Company”), dated [____]December 19, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx AlphaVest Acquisition Corp Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. AlphaVest Acquisition Corp. (the “Company”), dated [____]December 19, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. February 16, 2021 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCMORINGA ACQUISITION CORP. By: /s/ Xxxx Xxxxx Name: Xxxx Xxxxx Title: Chairman and Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] CEO SCHEDULE A PETRA ACQUISITION, INCMORINGA ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. 4,750,000 Moelis & Company LLC 5,000,000 Ladenburg 4,750,000 X. X. Xxxxxxxx & Co. Co., Inc. 2,500,000 500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionMoringa Acquisition Corp 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx 0xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Moringa Acquisition Corp (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionMoringa Acquisition Corp 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx 0xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Moringa Acquisition Corp (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as the underwriters in connection with the offering purchase and sale of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, stockholders or creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering purchase and sale of the Public Securities, Company’s securities either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between among the Underwriters Company and the CompanyUnderwriters, please so indicate in the space provided below for that purpose, whereupon this letter Agreement and the Underwriter’s acceptance shall constitute a binding agreement between usamong the Company and the Underwriters. Very Truly Yourstruly yours, PETRA ACQUISITIONDHT HOLDINGS, INC. By: Name: Title: Agreed to Accepted and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For agreed as of the date first written above, on behalf of themselves and as Representatives of the several other Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. A: By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Name Title SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units LIST OF UNDERWRITERS Name of Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 shares of common stock Total...................................................................................... SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionPERMITTED FREE WRITING PROSPECTUSES [•] SCHEDULE C CERTAIN INFORMATION [•] SCHEDULE D SUBSIDIARIES AND VESSELS Subsidiary Vessel Owned DHT Maritime, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (inone) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionAxx Tanker Corporation DHT Axx Cxxxx Tanker Corporation DHT Cxxxx Regal Unity Tanker Corporation DHT Regal Cxxxx Tanker Corporation DHT Cxxxx Sophie Tanker Corporation DHT Sophie Rxxxxxx Tanker Corporation DHT Rxxxxxx Ania Aframax Corporation DHT Ania London Tanker Corporation DHT London Newcastle Tanker Corporation DHT Newcastle DHT Eagle, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxDHT Eagle DHT Phoenix, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionInc. DHT Phoenix DHT Chartering, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (inone) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to preSCHEDULE E PERSONS REQUIRED TO DELIVER LOCK-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorUP AGREEMENTS

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCGREENROSE ACQUISITION CORP. By: /s/ Xxxxxxx X. Xxxxxx III Name: Xxxxxxx X. Xxxxxx III Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and IMPERIAL CAPITAL, LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxx Xxxxxx Name: Xxxx Xxxxxx Title: By LADENBURG XXXXXXXX Managing Director & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] General Counsel SCHEDULE A PETRA ACQUISITION, INCGREENROSE ACQUISITION CORP. 7,500,000 15,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital Imperial Capital, LLC 5,000,000 Ladenburg Xxxxxxxx & Co. 12,000,000 I-Bankers Securities, Inc. 2,500,000 3,000,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. Investor Presentation dated January 9, 2020 EXHIBIT A Form of Target Business Letter Petra AcquisitionGreenrose Acquisition Corp. 0000 Xxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx #000 Xxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Greenrose Acquisition Corp. (“Company”), dated [____]February 10, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionGreenrose Acquisition Corp. 0000 Xxxxxxxx Xxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxx #000 Xxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Greenrose Acquisition Corp. (“Company”), dated [____]February 10, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. CAMBRIDGE CAPITAL ACQUISITION CORPORATION By: /s/ Xxxxxxxx Xxxxxx Name: Xxxxxxxx Xxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Head of Investment Banking SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm CAMBRIDGE CAPITAL ACQUISITION CORPORATION 7,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. 5,900,000 Xxxxxx & Company, LLC 750,000 I-Bankers Securities, Inc. 250,000 Aegis Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 Corp 100,000 TOTAL 7,500,000 SCHEDULE B None. 7,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionCambridge Capital Acquisition Corporation 000 Xxxxx Xxxxxxx Xxxxx, Inc. 0 Xxxxx 000 Xxxx 00xx Xxxxxx Xxx XxxxXxxx Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cambridge Capital Acquisition Corporation (the “Company”), dated [____]December 17, 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00071,050,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionCambridge Capital Acquisition Corporation 000 Xxxxx Xxxxxxx Xxxxx, Inc. 0 Xxxxx 000 Xxxx 00xx Xxxxxx Xxx XxxxXxxx Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cambridge Capital Acquisition Corporation (the “Company”), dated [____]December 17, 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00071,050,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. ___________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. II By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_________, 20202021] SCHEDULE A PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. 7,500,000 Firm II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. Northland Securities, Inc.August 12, 2021Page 41 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCARMADA ACQUISITION CORP. I By: /s/ Sxxxxxx X. Xxxxxxx Name: Sxxxxxx X. Xxxxxxx Title: Chief Executive Officer & Chairman Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. NORTHLAND SECURITIES, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Jxxx Xxxxxxxx Name: Jxxx Xxxxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Head of Investment Banking [Signature Page to Underwriting Agreement, dated August [__]12, 20202021] SCHEDULE A PETRA ACQUISITION, INCARMADA ACQUISITION CORP. 7,500,000 Firm I 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Northland Securities, Inc. 2,500,000 14,950,000 B. Xxxxx Securities, Inc. 50,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Armada Acquisition Corp. I 8 Xxxxxxx Xxxxxx Xxx XxxxXxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Armada Acquisition Corp. I (the “Company”), dated [____]August 12, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to (A) modification of the substance or timing of the Company’s obligation to provide redemption rights as described in the Prospectus or (B) with respect to any other provision relating to stockholders’ rights or pre-Business Combination activityinitial business combinationactivity, (ii) to the Public Stockholders public shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination an initial business combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, a Business Combinationconsummates an initial business combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination buinses combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Armada Acquisition Corp. I 8 Xxxxxxx Xxxxxx Xxx XxxxXxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Armada Acquisition Corp. I (the “Company”), dated [____]August 12, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to (A) modification of the substance or timing of the Company’s obligation to provide redemption rights as described in the Prospectus or (B) with respect to any other provision relating to stockholders’ rights or pre-Business Combination initial business combination activity, (ii) to the Public Stockholders public shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination an initial business combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combinationan initial business combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account trust account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany’s securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yourstruly yours, PETRA ACQUISITION, INCASIA SPECIAL SITUATION ACQUISITION CORP. By: Name: Xxxxxx Xx Title: Chairman Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & COaccepted on the date first above written. INC. For themselves and MAXIM GROUP LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. underwriters By: Name: Xxxxxxxx X. Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Head of Investment Banking SCHEDULE A PETRA ACQUISITION, INCASIA SPECIAL SITUATION ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Number of Option Units to be Purchased Maxim Group LLC CRT Capital Group, LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 10,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionAsia Special Situation Acquisition Corp. P.O. Box 309GT, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxHouse South Church Street Xxxxxx Town, XX 00000 Grand Cayman Cayman Islands Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxxx Xx, Chairman Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionAsia Special Situation Acquisition Corp., Inc. (“CompanyASSAC”), dated [_____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company ASSAC has established the Trust AccountFund, initially in an amount of at least $75,750,000, 100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust AccountFund, the Company ASSAC may disburse monies from the Trust Account only: Fund only (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityASSAC, (ii) to for the Public Stockholders in connection with payment of taxes on interest earned on the Company’s liquidation amounts held in the event the Company is unable to consummate a Business Combination within the required time periodTrust Fund, or (iii) to ASSAC and the Company concurrently with, or Underwriters after it consummates, consummates a Business Combination. For and in consideration of the Company ASSAC agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account Fund (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company ASSAC and will not seek recourse against the Trust Account Fund for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionAsia Special Situation Acquisition Corp. P.O. Box 309GT, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxHouse South Church Street Xxxxxx Town, XX 00000 Grand Cayman Cayman Islands Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxxx Xx, Chairman Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionAsia Special Situation Acquisition Corp., Inc. (“CompanyASSAC”), dated [_____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company ASSAC has established the Trust AccountFund, initially in an amount of at least $75,750,000, 100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust AccountFund, the Company ASSAC may disburse monies from the Trust Account only: Fund only (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityASSAC, (ii) to for the Public Stockholders in connection with payment of taxes on interest earned on the Company’s liquidation amounts held in the event the Company is unable to consummate a Business Combination within the required time periodTrust Fund, or (iii) to ASSAC and the Company concurrently with, or Underwriters after it consummates a Business Combination. For and in consideration of the Company ASSAC agreeing to use the products or services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account Fund (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company negotiations, contracts or agreements with ASSAC and will not seek recourse against the Trust Account Fund for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorVendor EXHIBIT C Form of Director/Officer Letter Asia Special Situation Acquisition Corp. P.O. Box 309GT, Xxxxxx House South Church Street Xxxxxx Town, Grand Cayman Cayman Islands Attn: Xxxxxx Xx, Chairman Gentlemen: The undersigned officer or director of Asia Special Situation Acquisition Corp. (“ASSAC”) hereby acknowledges that ASSAC has established the Trust Fund, initially in an amount of at least $100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust Fund, ASSAC may disburse monies from the Trust Fund only (i) to the Public Stockholders in the event of the redemption of their shares or the dissolution and liquidation of ASSAC, (ii) for the payment of taxes on interest earned on the amounts held in the Trust Fund, or (iii) to ASSAC and the Underwriters after it consummates a Business Combination. The undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Fund (the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any contracts or agreements with ASSAC and will not seek recourse against the Trust Fund for any reason whatsoever. Notwithstanding the foregoing, such waiver shall not apply to any shares acquired by the undersigned in the public market. Print Name of Officer/Director Authorized Signature of Officer/Director

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. February 11, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCBITE ACQUISITION CORP. By: /s/ Xxxxxxx Xxxxxx Xxxxxxxx Name: Xxxxxxx Xxxxxx Xxxxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]February 11, 20202021] SCHEDULE A PETRA ACQUISITION, INCBITE ACQUISITION CORP. 7,500,000 Firm 17,500,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 EarlyBirdCapital, Inc. 14,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 3,450,000 Xxxxxx Xxxxxx & Co. LLC 50,000 TOTAL 7,500,000 17,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionBite Acquisition Corp. 00 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xx. 00X Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bite Acquisition Corp. (the “Company”), dated [____]February 11, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionBite Acquisition Corp. 00 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xx. 00X Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bite Acquisition Corp. (the “Company”), dated [____]February 11, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. RF ACQUISITION CORP II By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_________, 20202024] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm RF ACQUISITION CORP II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 Sch. A-1 SCHEDULE B [None. ] EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx RF Acquisition Corp II Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp II (the “Company”), dated [____]______, 2020 2024 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account including any monies distributed by the Company to Public Shareholders from the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx RF Acquisition Corp II Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp II (the “Company”), dated [____]______, 2020 2024 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account including any monies distributed by the Company to Public Shareholders from the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. __________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCBITE ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]________, 20202021] SCHEDULE A PETRA ACQUISITION, INCBITE ACQUISITION CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionBite Acquisition Corp. 30 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xx. 00X Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bite Acquisition Corp. (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionBite Acquisition Corp. 30 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xx. 00X Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Bite Acquisition Corp. (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL4, INC. By: Name: Dr. Avi X. Xxxx Title: Executive Chairman of the Board and Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX XXXXXXXXXXX & CO. INC. For themselves and ., as Representatives Representative of the several Underwriters named in on Schedule I A hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. NOMURA SECURITIES INTERNATIONAL, INC. ., as Representative of the several Underwriters named on Schedule A hereto By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITIONGIGCAPITAL4, INC. 7,500,000 26,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx Xxxxxxxxxxx & Co. Inc. 2,500,000 Nomura Securities International, Inc. TOTAL 7,500,000 26,000,000 SCHEDULE B NoneThe Company will pay the Underwriters $0.35 per Public Security as deferred underwriting commissions upon completion of the initial Business Combination as consideration for certain services to be performed by them as described in the Preliminary Prospectus. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”)SCHEDULE C Investor Presentation, dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor•] 2021 ANNEX A

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL6, INC. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX XXXXXXXXXXX & CO. INC. For themselves and ., as Representatives Representative of the several Underwriters named in on Schedule I A hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX XXXXXXX XXXXX & CO. INC. COMPANY, L.L.C., as Representative of the several Underwriters named on Schedule A hereto By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITIONGIGCAPITAL6, INC. 7,500,000 35,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx Xxxxxxxxxxx & Co. Inc. 2,500,000 Xxxxxxx Xxxxx & Company, L.L.C. TOTAL 7,500,000 35,000,000 SCHEDULE B NoneThe Company will pay the Underwriters $0.35 per Public Security as deferred underwriting commissions upon completion of the initial Business Combination as consideration for certain services to be performed by them as described in the Preliminary Prospectus. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”)SCHEDULE C Investor Presentation, dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor•] 2021 ANNEX A

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. ________, 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. DISTOKEN ACQUISITION CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm DISTOKEN ACQUISITION CORPORATION 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 4,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____]______, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,400,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,400,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and Company, the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially prevailing party(ies) in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies any such action shall be entitled to recover from the Trust Account only: (iother party(ies) to the Public Stockholders in the event all of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendorits reasonable therefor.

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. September 30, 2014 Page 42 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. DT Asia Investments Limited By: /s/Xxxxxxx X. Xxxxxx Name: Xxxxxxx X. Xxxxxx Title: President and Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: CEO [Signature Page to Underwriting Agreement, dated August [__]September 30, 20202014] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm DT ASIA INVESTMENTS LIMITED 6,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. 4,600,000 Aegis Capital LLC 5,000,000 Corp. 600,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 300,000 Xxxxxx & Company. 300,000 I-Bankers Securities, Inc. 200,000 TOTAL 7,500,000 SCHEDULE B None. 6,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionDT Asia Investments Limited 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx 0000 Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx X. Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DT Asia Investments Limited (the “Company”), dated [____]September 30, 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDT Asia Investments Limited 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx 0000 Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx X. Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DT Asia Investments Limited (the “Company”), dated [____]September 30, 2020 2014 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00061,200,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. December 10, 2018 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCSXXXXXXX SPECIAL PURPOSE ACQUISITION CORP. By: /s/ Gxxxxx Xxxxxxxx Name: Gxxxxx Xxxxxxxx Title: Director Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] CEO SCHEDULE A PETRA ACQUISITION, INCSXXXXXXX SPECIAL PURPOSE ACQUISITION CORP. 7,500,000 13,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. 7,200,000 BTIG, LLC 5,000,000 3,250,000 Ladenburg Xxxxxxxx Txxxxxxx & Co. Inc. 2,500,000 1,300,000 I-Bankers Securities, Inc. 1,250,000 TOTAL 7,500,000 13,000,000 SCHEDULE B None. Sxxxxxxx Special Purpose Acquisition Corp. IPO Presentation Overview, November 2018 EXHIBIT A Form of Target Business Letter Petra AcquisitionSxxxxxxx Special Purpose Acquisition Corp. 800 Xxxxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx 000 Xxx XxxxXxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Sxxxxxxx Special Purpose Acquisition Corp. (“Company”), dated [____]December 10, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000130,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionSxxxxxxx Special Purpose Acquisition Corp. 800 Xxxxxxxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx 000 Xxx XxxxXxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Sxxxxxxx Special Purpose Acquisition Corp. (“Company”), dated [____]December 10, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000130,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. [●], 2017 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. FORUM MERGER CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__●], 20202017] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm FORUM MERGER CORPORATION 12,500,000 Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. [●] FBR Capital LLC 5,000,000 Ladenburg Xxxxxxxx Markets & Co. Inc. 2,500,000 [●] TOTAL 7,500,000 SCHEDULE B None. 12,500,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionForum Merger Corporation c/o Forum Investors I, Inc. 0 LLC 000 Xxxx 00xx Xxxxxx Xxxxxx, 0xx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Forum Merger Corporation (the “Company”), dated [____●], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000126,250,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionForum Merger Corporation c/o Forum Investors I, Inc. 0 LLC 000 Xxxx 00xx Xxxxxx Xxxxxx, 0xx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Forum Merger Corporation (the “Company”), dated [____●], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000126,250,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. _________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCFINNOVATE ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCFINNOVATE ACQUISITION CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 15,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Finnovate Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Finnovate Acquisition Corp. (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000153,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Finnovate Acquisition Corp. Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Finnovate Acquisition Corp. (the “Company”), dated [____]_____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000153,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. ________, 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDD3 ACQUISITION CORP. II By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]______, 2020] SCHEDULE A PETRA ACQUISITION, INCDD3 ACQUISITION CORP. 7,500,000 Firm II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionDD3 Acquisition Corp. II Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx, Xxxxxxxx 000 Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. II (the “Company”), dated [____]____, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDD3 Acquisition Corp. II Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx, Xxxxxxxx 000 Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. II (the “Company”), dated [____]____, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCRF ACQUISITION CORP. By: /s/ Tse Mxxx Xx Name: Tse Mxxx Xx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Chief Executive Officer SCHEDULE A PETRA ACQUISITION, INCRF ACQUISITION CORP. 7,500,000 10,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg EarlyBirdCapital, Inc. 10,000,000 Units TOTAL 10,000,000 Schedule A-0 XXXXXXXX X Xxxx Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. X-0 EXHIBIT A Form of Target Business Letter Petra AcquisitionRF Acquisition Corp. c/o Puglisi & Associates 800 Xxxxxxx Xxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX Xxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp. (“Company”), dated [____]March 15, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business Exh. A-1 EXHIBIT B Form of Vendor Letter Petra AcquisitionRF Acquisition Corp. c/o Puglisi & Associates 800 Xxxxxxx Xxxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX Xxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp. (“Company”), dated [____]March 15, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorVendor Exh. B-1

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: /s/ Xxxxxxx Xxxxxxxx Name: Xxxxxxx Xxxxxxxx Title: CEO Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxx Xxxxxx Name: Xxxxx Xxxxxx Title: Managing Director By LADENBURG XXXXXXXX & CO. INC. By: /s/ Xxxxx Xxxxxx Name: Xxxxx Xxxxxx Title: Head of Capital Markets [Signature Page to Underwriting Agreement, dated August [__]October 7, 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 7,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 2,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 2,450,000 Northland Capital Markets 1,400,000 Xxxxxxx & Xxxxxx LLC 1,150,000 TOTAL 7,500,000 7,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00070,700,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00070,700,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. February 3, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCASTREA ACQUISITION CORP. By: /s/ Xxxxxx Xxxxxxxx Name: Xxxxxx Xxxxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Head of Investment Banking [Signature Page to Underwriting Agreement, dated August [__]February 3, 20202021] EarlyBirdCapital, Inc. February 3, 2021 SCHEDULE A PETRA ACQUISITION, INCASTREA ACQUISITION CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 15,000,000 EarlyBirdCapital, Inc. February 3, 2021 SCHEDULE B None. [to be finalized] EarlyBirdCapital, Inc. February 3, 2021 EXHIBIT A Form of Target Business Letter Petra AcquisitionAstrea Acquisition Corp. 00 Xxxxx Xxxx Xxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxx. 0000 Key Xxxxxxxx, XX Xxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Astrea Acquisition Corp. (the “Company”), dated [____]____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EarlyBirdCapital, Inc. February 3, 2021 EXHIBIT B Form of Vendor Letter Petra AcquisitionAstrea Acquisition Corp. 00 Xxxxx Xxxx Xxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxx. 0000 Key Xxxxxxxx, XX Xxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Astrea Acquisition Corp. (the “Company”), dated [____]____, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000150,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL5, INC. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX XXXXXXXXXXX & CO. INC. For themselves and ., as Representatives Representative of the several Underwriters named in on Schedule I A hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX XXXXXXX XXXXX & CO. INC. COMPANY, L.L.C., as Representative of the several Underwriters named on Schedule A hereto By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITIONGIGCAPITAL5, INC. 7,500,000 35,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx Xxxxxxxxxxx & Co. Inc. 2,500,000 Xxxxxxx Xxxxx & Company, L.L.C. TOTAL 7,500,000 35,000,000 SCHEDULE B NoneThe Company will pay the Underwriters $0.35 per Public Security as deferred underwriting commissions upon completion of the initial Business Combination as consideration for certain services to be performed by them as described in the Preliminary Prospectus. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”)SCHEDULE C Investor Presentation, dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor●] 2021 ANNEX A

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. Xxxxxxxx Inc. [●], 2022 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDORCHESTER CAPITAL ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. ., as Representative of the several Underwriters By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCDORCHESTER CAPITAL ACQUISITION CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg EarlyBirdCapital, Inc. Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 15,000,000 SCHEDULE B [None. .] EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Dorchester Capital Acquisition Corp. 000 Xxxx 00xx Xxxxxx Xxx Xxxxx 0000 Xxxxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Dorchester Capital Acquisition Corp. (the “Company”), dated [____●], 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000153,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, ; or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Dorchester Capital Acquisition Corp. 000 Xxxx 00xx Xxxxxx Xxx Xxxxx 0000 Xxxxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Dorchester Capital Acquisition Corp. (the “Company”), dated [____●], 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000153,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, ; or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. _______, 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. LIGHTJUMP ACQUISITION CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_____, 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm LIGHTJUMP ACQUISITION CORPORATION 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 LightJump Acquisition Corporation 0000 Xxxx 00xx Xxxxxx Xxx Xxxx Xxxx Xxxxx 000 Xxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LightJump Acquisition Corporation (the “Company”), dated [____]___, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 LightJump Acquisition Corporation 0000 Xxxx 00xx Xxxxxx Xxx Xxxx Xxxx Xxxxx 000 Xxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LightJump Acquisition Corporation (the “Company”), dated [____]___, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONEARLYBIRDCAPITAL, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule GESHER I hereto By LIFESCI CAPITAL LLCACQUISITION CORP. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCGESHER I ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 [__] TOTAL 7,500,000 15,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionGesher I Acquisition Corp. Hagag Towers Xxxxx Xxxxx, Inc. 0 Xxxx 00xx Xxxxx 00 Xxxxxx 00 Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Gesher I Acquisition Corp. (the “Company”), dated [______ __], 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended Memorandum and Restated Certificate Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionGesher I Acquisition Corp. Hagag Towers Xxxxx Xxxxx, Inc. 0 Xxxx 00xx Xxxxx 00 Xxxxxx 00 Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Gesher I Acquisition Corp. (the “Company”), dated [______ __], 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended Memorandum and Restated Certificate Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. ___________, 2022 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. II By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_________, 20202022] SCHEDULE A PETRA ACQUISITION, INCLIV CAPITAL ACQUISITION CORP. 7,500,000 Firm II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionLIV Capital Acquisition Corp. II c/o LIV Capital Torre Virreyes Pedregal Xx. 00, Inc. 0 Xxxx 00xx 0-000 Xxx. Xxxxxx Xxx Xxxxdel Rey México, XX 00000 Attn: Xxxxxxx Xxxxxxxx CDMX, C.P. 11040 Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. LIV Capital Acquisition Corp. II (the “Company”), dated [____]_______, 2020 2022 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. _____, 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCINTERPRIVATE ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INCINTERPRIVATE ACQUISITION CORP. 7,500,000 17,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 [_____] I-Bankers Securities, Inc. [_____] TOTAL 7,500,000 17,500,000 SCHEDULE B None. [_____] EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx InterPrivate Acquisition Corp. 0000 Xxxxxx xx xxx Xxxxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. InterPrivate Acquisition Corp. (“Company”), dated [____]_, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx InterPrivate Acquisition Corp. 0000 Xxxxxx xx xxx Xxxxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. InterPrivate Acquisition Corp. (“Company”), dated [____]_, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000175,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. [_____], 2017 Page 41 of 42 [Signature Page Follows] EarlyBirdCapital, Inc. [_____], 2017 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCBLACK RIDGE ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [_____], 20202017] SCHEDULE A PETRA ACQUISITION, INCBLACK RIDGE ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. Investor Presentation dated August 2017 EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Black Ridge Acquisition Corp. 100 Xxxxx 0xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Black Ridge Acquisition Corp. (the “Company”), dated [_____], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or upon an amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityas described in the Prospectus, (ii) to the Company in limited amounts for its income and other tax obligations, (iii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iiiiv) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Black Ridge Acquisition Corp. 100 Xxxxx 0xx Xxxxxx Xxx XxxxXxxxx 000 Xxxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Black Ridge Acquisition Corp. (the “Company”), dated [_____], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or upon an amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityas described in the Prospectus, (ii) to the Company in limited amounts for its income and other tax obligations, (iii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iiiiv) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. June 19, 2018 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. TWELVE SEAS INVESTMENT COMPANY By: /s/ Xxxxxxx X. Xxxxxx Name: Xxxxxxx X. Xxxxxx Title: Chief Financial Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Chief Executive Officer [Signature Page to Underwriting Agreement, dated August [__]June 19, 20202018] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm TWELVE SEAS INVESTMENT COMPANY 18,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 EarlyBirdCapital, Inc. 7,680,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 4,800,000 X. Xxxxx FBR, Inc.. 4,200,000 I-Bankers Securities, Inc. 1,320,000 TOTAL 7,500,000 18,000,000 SCHEDULE B None. Investor presentation, June 2018 EXHIBIT A Form of Target Business Letter Petra AcquisitionTwelve Seas Investment Company 00/00 Xxx Xxxxxxxxxx Xxxxxx Xxxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx X0X 0XX Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Twelve Seas Investment Company (the “Company”), dated [____]June 19, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000180,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionTwelve Seas Investment Company 00/00 Xxx Xxxxxxxxxx Xxxxxx Xxxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxXxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx X0X 0XX Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Twelve Seas Investment Company (the “Company”), dated [____]June 19, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000180,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. October __, 2013 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCQUARTET MERGER CORP. By: Name: Xxxx X. Xxxxxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 20202013] SCHEDULE A PETRA ACQUISITION, INCQUARTET MERGER CORP. 7,500,000 Firm 8,400,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 8,400,000 EXHIBIT A Form of Legal Opinion EXHIBIT B Form of Target Business Letter Petra AcquisitionQuartet Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Xxxx X. Xxxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Quartet Merger Corp. (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000$ , for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B C Form of Vendor Letter Petra AcquisitionQuartet Merger Corp. 000 Xxxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx Xxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Xxxx X. Xxxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Quartet Merger Corp. (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000$ , for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL3, INC. By: /s/ Dr. Avi X. Xxxx Name: Dr. Avi X. Xxxx Title: Executive Chairman of the Board and Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. NOMURA SECURITIES INTERNATIONAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in on Schedule I A hereto By LIFESCI CAPITAL LLC. By: /s/ Xxxxx Xxxxxxx Name: Xxxxx Xxxxxxx Title: By LADENBURG XXXXXXXX Managing Director XXXXXXXXXXX & CO. INC. ., as Representative of the several Underwriters named on Schedule A hereto By: /s/ Xxxxx Xxxxxxx Name: Xxxxx Xxxxxxx Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Managing Director SCHEDULE A PETRA ACQUISITIONGIGCAPITAL3, INC. 7,500,000 20,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx Nomura Securities International, Inc. 10,200,000 Xxxxxxxxxxx & Co. Inc. 2,500,000 6,800,000 Odeon Capital Group LLC 3,000,000 TOTAL 7,500,000 20,000,000 42 SCHEDULE B NoneThe Company will pay the Underwriters $0.40 per Public Security as deferred underwriting commissions upon completion of the initial Business Combination as consideration for certain services to be performed by them as described in the Preliminary Prospectus. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”)SCHEDULE C Investor Presentation, dated [____]May 4, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorANNEX A BCMS Indemnification

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. By: Name: Title: Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August July [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 12,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 12,500,000 SCHEDULE B None. None EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 5 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 5 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000125,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. _____________, 2013 Page 45 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. CAMBRIDGE CAPITAL ACQUISITION CORPORATION By: Name: Xxxxxxxx Xxxxxx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 20202013] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm CAMBRIDGE CAPITAL ACQUISITION CORPORATION 7,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. Xxxxxx & Company, LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 7,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionCambridge Capital Acquisition Corporation 000 Xxxxx Xxxxxxx Xxxxx, Inc. 0 Xxxxx 000 Xxxx 00xx Xxxxxx Xxx XxxxXxxx Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cambridge Capital Acquisition Corporation (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00071,050,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionCambridge Capital Acquisition Corporation 000 Xxxxx Xxxxxxx Xxxxx, Inc. 0 Xxxxx 000 Xxxx 00xx Xxxxxx Xxx XxxxXxxx Xxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Cambridge Capital Acquisition Corporation (the “Company”), dated [____], 2020 2013 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00071,050,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany’s securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yourstruly yours, PETRA ACQUISITION, INCASIA SPECIAL SITUATION ACQUISITION CORP. Date: By: Name: Xxxxxx Xx Title: Chairman Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & COaccepted on the date first above written. INC. For themselves and MAXIM GROUP LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. underwriters By: Name: Xxxxxxxx X. Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] Head of Investment Banking SCHEDULE A PETRA ACQUISITION, INCASIA SPECIAL SITUATION ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital Maxim Group LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. 10,000,000 EXHIBIT A Form of Target Business Letter Petra AcquisitionAsia Special Situation Acquisition Corp. P.O. Box 309GT, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxHouse South Church Street Xxxxxx Town, XX 00000 Grand Cayman Cayman Islands Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxxx Xx, Chairman Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionAsia Special Situation Acquisition Corp., Inc. (“CompanyASSAC”), dated [_____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company ASSAC has established the Trust AccountFund, initially in an amount of at least $75,750,000, 100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust AccountFund, the Company ASSAC may disburse monies from the Trust Account only: Fund only (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination ASSAC or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to ASSAC and the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or Underwriters after it consummates, consummates a Business Combination. For and in consideration of the Company ASSAC agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account Fund (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company ASSAC and will not seek recourse against the Trust Account Fund for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business 47 EXHIBIT B Form of Vendor Letter Petra AcquisitionAsia Special Situation Acquisition Corp. P.O. Box 309GT, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxHouse South Church Street Xxxxxx Town, XX 00000 Grand Cayman Cayman Islands Attn: Xxxxxxx Xxxxxxxx Ladies and Xxxxxx Xx, Chairman Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionAsia Special Situation Acquisition Corp., Inc. (“CompanyASSAC”), dated [_____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company ASSAC has established the Trust AccountFund, initially in an amount of at least $75,750,000, 100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust AccountFund, the Company ASSAC may disburse monies from the Trust Account only: Fund only (i) to the Public Stockholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination ASSAC or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to ASSAC and the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or Underwriters after it consummates a Business Combination. For and in consideration of the Company ASSAC agreeing to use the products or services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account Fund (each, a the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company negotiations, contracts or agreements with ASSAC and will not seek recourse against the Trust Account Fund for any reason whatsoever. Print Name of Vendor Authorized Signature of VendorVendor 48 EXHIBIT C Form of Director/Officer Letter Asia Special Situation Acquisition Corp. P.O. Box 309GT, Xxxxxx House South Church Street Xxxxxx Town, Grand Cayman Cayman Islands Attn: Xxxxxx Xx, Chairman Gentlemen: The undersigned officer or director of Asia Special Situation Acquisition Corp. (“ASSAC”) hereby acknowledges that ASSAC has established the Trust Fund, initially in an amount of at least $100,000,000 for the benefit of the Public Stockholders and the underwriters of ASSAC’s initial public offering (the “Underwriters”) and that, except for up to $2,000,000 of the interest earned on the amounts held in the Trust Fund, ASSAC may disburse monies from the Trust Fund only (i) to the Public Stockholders in the event of the redemption of their shares or the dissolution and liquidation of ASSAC or (ii) to ASSAC and the Underwriters after it consummates a Business Combination. The undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Fund (the “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any contracts or agreements with ASSAC and will not seek recourse against the Trust Fund for any reason whatsoever. Notwithstanding the foregoing, such waiver shall not apply to any shares acquired by the undersigned in the public market. Print Name of Officer/Director Authorized Signature of Officer/Director

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. __________, 2018 Page 42 of 42 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCOPES ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]_______, 20202018] SCHEDULE A PETRA ACQUISITION, INCOPES ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. Investor Presentation dated January 2018 EXHIBIT A Form of Target Business Letter Petra AcquisitionOpes Acquisition Corp. Park Plaza Torre I Javxxx Xxxxxx Xxerra 540, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxOf. 103 Col. Santa Fe 01210 Mexico City, XX 00000 Attn: Xxxxxxx Xxxxxxxx Mexico Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Opes Acquisition Corp. (the “Company”), dated [____]_____, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or upon an amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityas described in the Prospectus, (ii) to the Company in limited amounts for its income and other tax obligations, (iii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iiiiv) to the Company concurrently with, or after after, it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionOpes Acquisition Corp. Park Plaza Torre I Javxxx Xxxxxx Xxerra 540, Inc. 0 Xxxx 00xx Xxxxxx Xxx XxxxOf. 103 Col. Santa Fe 01210 Mexico City, XX 00000 Attn: Xxxxxxx Xxxxxxxx Mexico Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Opes Acquisition Corp. (the “Company”), dated [____]_____, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000101,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or upon an amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activityas described in the Prospectus, (ii) to the Company in limited amounts for its income and other tax obligations, (iii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iiiiv) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. NOVUS CAPITAL CORPORATION By: /s/Xxxxxxx Xxxxxxx Name: Xxxxxxx Xxxxxxx Title: Chief Financial Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/Xxxxxx Xxxxxx Name: Xxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] CEO SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 NOVUS CAPITAL CORPORATION 10,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 EarlyBirdCapital, Inc. 8,000,000 I-Bankers Securities, Inc. 1,500,000 Ladenburg Xxxxxxxx & $ Co. Inc. 2,500,000 500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Novus Capital Corporation 0000 Xxxxxxx Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Novus Capital Corporation (“Company”), dated [____]as of May 14, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for a portion of the interest earned on the amounts held in the Trust AccountAccount releasable to the Company for taxes, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Novus Capital Corporation 0000 Xxxxxxx Xxxx 00xx Xxxxxx Xxx XxxxXxxxxxxxxxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Novus Capital Corporation (“Company”), dated [____]as of May 14, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders and that, except for a portion of the interest earned on the amounts held in the Trust AccountAccount releasable to the Company for taxes, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. _____, 2018 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCGXXX INDUSTRIAL CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]___, 20202018] SCHEDULE A PETRA ACQUISITION, INCGXXX INDUSTRIAL CORP. 7,500,000 22,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionEarlyBirdCapital, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, _] Oxxxxxxxxxx & Co. Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [_____] I-Bankers Securities, Inc. [_____] [_____] [_____] TOTAL 22,500,000 SCHEDULE B [_____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. , 2020 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. DISTOKEN ACQUISITION CORPORATION By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm DISTOKEN ACQUISITION CORPORATION 4,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 TOTAL 7,500,000 4,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____]______, 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Distoken Acquisition Corporation Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Distoken Acquisition Corporation (the “Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00040,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-pre- Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] EarlyBirdCapital, Inc. __________, 2021 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCMORINGA ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]________, 20202021] SCHEDULE A PETRA ACQUISITION, INCMORINGA ACQUISITION CORP. 7,500,000 Firm 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital EarlyBirdCapital, Inc. Moelis & Company LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 10,000,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra AcquisitionMoringa Acquisition Corp 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx 0xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Moringa Acquisition Corp (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionMoringa Acquisition Corp 000 Xxxx Xxxxxx, Inc. 0 Xxxx 00xx Xxxxxx 0xx Xxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Moringa Acquisition Corp (the “Company”), dated [____]______, 2020 2021 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public SecuritiesCompany’s securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public SecuritiesCompany’s securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public SecuritiesCompany’s securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. 47 Maxim Group LLC , 2007 Page 48 of 48 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCSEANERGY MARITIME CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and MAXIM GROUP LLC, as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Cxxxxxxx X. Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: Director of Investment Banking [Signature Page to Underwriting Agreement, dated August [__], 20202007] SCHEDULE A PETRA ACQUISITION, INCSEANERGY MARITIME CORP. 7,500,000 Firm 15,000,000 Units Underwriter Number of Firm Units Underwriter to be Purchased LifeSci Capital Maxim Group LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Seanergy Maritime Corp. 600 Xxxxx Xxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Seanergy Maritime Corp. (the “Company”), dated [____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, 150,000,000 for the benefit of the Public Stockholders Shareholders and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for a portion of the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; (ii) to the Public Stockholders in connection with Shareholder from the Company’s liquidation in interest income earned on the event Trust Account, as determined by the Company is unable to consummate a Business Combination within the required time period, Board of Directors; or (iiiii) to the Company concurrently with, or and the Underwriters after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Seanergy Maritime Corp. 600 Xxxxx Xxxxxx Xxx Xxxx, XX Xxx Xxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. Seanergy Maritime Corp. (the “Company”), dated [____], 2020 2007 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, 150,000,000 for the benefit of the Public Stockholders Shareholders and the underwriters of the Company’s initial public offering (the “Underwriters”) and that, except for a portion of the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation or the dissolution and liquidation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, ; (ii) to the Public Stockholders in connection with Shareholder from the Company’s liquidation in interest income earned on the event Trust Account, as determined by the Company is unable to consummate a Business Combination within the required time period, Board of Directors; or (iiiii) to the Company concurrently with, or and the Underwriters after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc.__________, 2018Page 43 of 45 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCDD3 ACQUISITION CORP. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__]___________, 20202018] SCHEDULE A PETRA ACQUISITION, INCDD3 ACQUISITION CORP. 7,500,000 Firm 5,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC EarlyBirdCapital, Inc. TOTAL 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. Investor Presentation, September 2018 EXHIBIT A Form of Target Business Letter Petra AcquisitionDD3 Acquisition Corp. c/o DD3 Mex Acquisition Corp Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. (the “Company”), dated [____]____, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionDD3 Acquisition Corp. c/o DD3 Mex Acquisition Corp Pxxxxxxx 00, Inc. 0 Xxxx 00xx 0xx Xxxxx Xxxxxxx Xxxxxx Xxx del Rey, Del. Mxxxxx Xxxxxxx 00000 Xxxxxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Xxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. DD3 Acquisition Corp. (the “Company”), dated [____]______, 2020 2018 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate Memorandum and Articles of Incorporation Association relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s 's length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. EarlyBirdCapital, Inc. [_____], 2017 If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA XXXXXX OAKWOOD TECHNOLOGY ACQUISITION, INC. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [_____], 20202017] SCHEDULE A PETRA XXXXXX OAKWOOD TECHNOLOGY ACQUISITION, INC. 7,500,000 Firm 5,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC EarlyBirdCapital, Inc. [______] TOTAL 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. [Attached] EXHIBIT A Form of Target Business Letter Petra Xxxxxx Oakwood Technology Acquisition, Inc. 0 c/x Xxxxxx Oakwood Investments, LLC 00 Xxxx 00xx Xxxxxx 0xx Xxx. Xxx XxxxXxxxx, XX Xxxxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Xxxxxx Oakwood Technology Acquisition, Inc. (the “Company”), dated [_____], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Xxxxxx Oakwood Technology Acquisition, Inc. 0 c/x Xxxxxx Oakwood Investments, LLC 00 Xxxx 00xx Xxxxxx 0xx Xxx. Xxx XxxxXxxxx, XX Xxxxxxxxxx 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Xxxxxx Oakwood Technology Acquisition, Inc. (the “Company”), dated [_____], 2020 2017 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,00050,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. [Signature Page Follows] If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITIONGIGCAPITAL2, INC. By: Name: Title: Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITIONGIGCAPITAL2, INC. 7,500,000 13,000,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci EarlyBirdCapital, Inc. [_____] Northland Securities, Inc. [_____] Odeon Capital Group LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 [_____] TOTAL 7,500,000 13,000,000 SCHEDULE B None. [_____] EXHIBIT A Form of Target Business Letter Petra AcquisitionGigCapital2, Inc. 0 0000 X. Xxxxxxxx Xx., Xxxxx 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionGigCapital2, Inc. (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000130,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra AcquisitionGigCapital2, Inc. 0 0000 X. Xxxxxxxx Xx., Xxxxx 000 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra AcquisitionGigCapital2, Inc. (“Company”), dated [____], 2020 2019 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000130,000,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and Company, the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters Representative and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INCBUKIT JALIL GLOBAL ACQUISITION 1 LTD. By: /s/ Xxxx Xxxx “Xxxx” Foo Name: Xxxx Xxxx “Xxxx” Foo Title: Chief Executive Officer Agreed to and Accepted: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. INC. For themselves and accepted as Representatives of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: Name: Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: [Signature Page to Underwriting Agreement, dated August [__], 2020] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. Inc. 2,500,000 TOTAL 7,500,000 SCHEDULE B None. EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates, a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. (“Company”), dated [____], 2020 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000, for the benefit of the Public Stockholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders in the event of the conversion of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendordate first written above:

No Fiduciary Relationship. The Company hereby acknowledges that the Underwriters are acting solely as underwriters in connection with the offering of the Public Securities. The Company further acknowledges that the Underwriters are acting pursuant to a contractual relationship created solely by this Agreement entered into on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholdersshareholders, creditors or any other person in connection with any activity that the Underwriters may undertake or have undertaken in furtherance of the offering of the Public Securities, either before or after the date hereof. The Underwriters hereby expressly disclaim any fiduciary or similar obligations to the Company, either in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions, and the Company hereby confirms its understanding and agreement to that effect. The Company and the Underwriters agree that they are each responsible for making their own independent judgments with respect to any such transactions, and that any opinions or views expressed by the Underwriters to the Company regarding such transactions, including but not limited to any opinions or views with respect to the price or market for the Public Securities, do not constitute advice or recommendations to the Company. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriters with respect to any breach or alleged breach of any fiduciary or similar duty to the Company in connection with the transactions contemplated by this Agreement or any matters leading up to such transactions. If the foregoing correctly sets forth the understanding between the Underwriters and the Company, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding agreement between us. Very Truly Yours, PETRA ACQUISITION, INC. RF ACQUISITION CORP II By: /s/ Tse Mxxx Xx Name: Txx Mxxx Xx Title: Chief Executive Officer Agreed to and Acceptedaccepted as of the date first written above: LIFESCI CAPITAL LLC LADENBURG XXXXXXXX & CO. EARLYBIRDCAPITAL, INC. For themselves and ., as Representatives Representative of the several Underwriters named in Schedule I hereto By LIFESCI CAPITAL LLC. By: /s/ Sxxxxx Xxxxxx Name: Sxxxxx Xxxxxx Title: By LADENBURG XXXXXXXX & CO. INC. By: Name: Title: CEO [Signature Page to Underwriting Agreement, dated August [__]May 16, 20202024] SCHEDULE A PETRA ACQUISITION, INC. 7,500,000 Firm RF ACQUISITION CORP II 10,000,000 Units Underwriter Number of Firm Units to be Purchased LifeSci Capital LLC 5,000,000 Ladenburg Xxxxxxxx & Co. EarlyBirdCapital, Inc. 2,500,000 9,500,000 Revere Securities 250,000 BenjaminSecurities,Inc. 250,000 TOTAL 7,500,000 10,000,000 Sch. A-1 SCHEDULE B None. None EXHIBIT A Form of Target Business Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx RF Acquisition Corp II Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp II (the “Company”), dated [____]May 16, 2020 2024 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates, consummates a Business Combination. For and in consideration of the Company agreeing to evaluate the undersigned for purposes of consummating a Business Combination with it, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account including any monies distributed by the Company to Public Shareholders from the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Target Business Authorized Signature of Target Business EXHIBIT B Form of Vendor Letter Petra Acquisition, Inc. 0 Xxxx 00xx Xxxxxx Xxx Xxxx, XX 00000 Attn: Xxxxxxx Xxxxxxxx RF Acquisition Corp II Ladies and Gentlemen: Reference is made to the Final Prospectus of Petra Acquisition, Inc. RF Acquisition Corp II (the “Company”), dated [____]May 16, 2020 2024 (the “Prospectus”). Capitalized terms used and not otherwise defined herein shall have the meanings assigned to them in the Prospectus. We have read the Prospectus and understand that the Company has established the Trust Account, initially in an amount of at least $75,750,000100,500,000, for the benefit of the Public Stockholders Shareholders and that, except for the interest earned on the amounts held in the Trust Account, the Company may disburse monies from the Trust Account only: (i) to the Public Stockholders Shareholders in the event of the conversion redemption of their shares upon consummation of a Business Combination or amendment to the Company’s Amended and Restated Certificate of Incorporation relating to pre-Business Combination activity, (ii) to the Public Stockholders Shareholders in connection with the Company’s liquidation in the event the Company is unable to consummate a Business Combination within the required time period, period or (iii) to the Company concurrently with, or after it consummates a Business Combination. For and in consideration of the Company agreeing to use the services of the undersigned, the undersigned hereby agrees that it does not have any right, title, interest or claim of any kind in or to any monies in the Trust Account including any monies distributed by the Company to Public Shareholders from the Trust Account (each, a “Claim”) and hereby waives any Claim it may have in the future as a result of, or arising out of, any services provided to the Company and will not seek recourse against the Trust Account for any reason whatsoever. Print Name of Vendor Authorized Signature of Vendor