EXHIBIT 99.4
JOINT FILING UNDERTAKING
The undersigned, being duly authorized thereunto, hereby execute this
agreement as an exhibit to this Amendment No. 1 to Schedule 13D to evidence the
agreement of the below-named parties, in accordance with the rules promulgated
pursuant to the Securities Exchange Act of 1934, to file this Amendment No. 1 to
Schedule 13D jointly on behalf of each such party.
The execution and filing of this agreement shall not be construed as an
admission that the below-named parties are a group, or have agreed to act as a
group.
Dated: March 8, 2006 BERKSHIRE FUND IV, LIMITED PARTNERSHIP
By: Fourth Berkshire Associates LLC,
its General Partner
By: /s/Xxxxxxx X. Xxxxx
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Name: Xxxxxxx X. Xxxxx
Title: Managing Member
BERKSHIRE FUND V, LIMITED PARTNERSHIP
By: Fifth Berkshire Associates LLC,
its General Partner
By: /s/Xxxxxxx X. Xxxxx
-------------------
Name: Xxxxxxx X. Xxxxx
Title: Managing Member
BERKSHIRE INVESTORS LLC
By: /s/Xxxxxxx X. Xxxxx
-------------------
Name: Xxxxxxx X. Xxxxx
Title: Managing Director
