Each series issued by the master trust shares the cash flow and therefore the credit risk of one pool of credit card receivables of the issuer.     1Letting M denote the number of months after loan origination, the SMM rate can be calculated from the ABS rate using the following formula: ABS = ---------------------------------------------- 1 - ABS ´ ( M - 1 )   where the ABS and SMM rates are expressed in decimal form. 2ThomasZimmermanandLeoBurrell,"AutoLoan-BackedSecurities,"Chapter4 in Anand K. Bhattacharya and Frank J. Fabozzi (eds.) Asset-Backed Securities (New Hope, PA: Frank J. Fabozzi Associates, 1996).       For a pool of credit card receivables, the cash flow consists of finance charges collected, fees, interchange, and principal. Finance charges col- lected represent the periodic interest the credit card borrower is charged based on the unpaid balance after the grace period. Fees include late pay- ment fees and any annual membership fees. For Visa and MasterCard, a payment is made to originators. This payment is called interchange and is made to the originator for providing funding and accepting risk during the grace period. The principal is the amount of the borrowed funds repaid. Interest to security holders is paid periodically (e.g, monthly, quarterly, or semiannually). The interest rate may be fixed or floating. A credit card receivable-backed security is a non-amortizing secu- rity. For a specified period of time, referred to as the lockout period or revolving period, the principal payments made by credit card borrowers comprising the pool are retained by the trustee and reinvested in addi- tional receivables. The lockout period can vary from 18 months to 10 years. So, during the lockout period, the cash flow that is paid out is based on finance charges collected and fees. After the lockout period, the principal is no longer reinvested but paid to investors. This period is referred to as the principal-amortization period. There are three different amortization structures that have been used in credit-card receivable-backed security structures: (1) passthrough structure, (2) controlled-amortization structure, and (3) bullet-payment structure.     In a passthrough structure, the principal cash flows from the credit card accounts are paid to the security holders on a pro rata basis. In a controlled-amortization structure, a scheduled principal amount is estab- lished. The scheduled principal amount is sufficiently low so that the