Portfolio Yield means, with respect to any Monthly Period, the annualized percentage equivalent of a fraction, the numerator of which is (a) the amount of Available Funds allocated to the MBNAseries pursuant to Section 501 of the Indenture, plus (b) any Interest Funding sub-Account Earnings on the related Transfer Date, plus (c) any amounts to be treated as MBNAseries Available Funds pursuant to Sections 3.20(d) and 3.27(a) of the Indenture Supplement, plus (d) the MBNAseries Servicer Interchange for such Monthly Period, minus (e) the excess, if any, of the sum of the PFA Prefunding Earnings Shortfall plus the PFA Accumulation Earnings Shortfall over the sum of the aggregate amount to be treated as MBNAseries Available Funds for such Monthly Period pursuant to Sections 3.04(a)(ii) and 3.25(a) of the Indenture Supplement plus any other amounts applied to cover earnings shortfalls on amounts in the Principal Funding sub-Account for any tranche of MBNAseries Notes for such Monthly Period, minus (f) the MBNAseries Investor Default Amount for such Monthly Period, and the denominator of which is the Weighted Average Available Funds Allocation Amount for the MBNAseries for such Monthly Period.