ties – Interest Weighted Securities and Non-VRDI Securities" in the Base Offering Circular. Although the tax treatment of Interest Weighted Securities is not entirely certain, Holders of the Interest Weighted Securities should expect to accrue all income on these Securities (other than income attributable to market discount or de minimis market discount) under the OID rules based on the expected payments on these Securities at the prepayment assumption described below. In addition to  the Regular Securities described in the preceding two paragraphs, based on anticipated prices (including accrued interest), the assumed Mortgage Loan characteristics, the prepayment assumption described below and, in the case of the Class FA, FB and FC Securities Classes, the constant LIBOR value described below, Class PA is expected to be issued with OID. Prospective investors in the Regular Securities should be aware, however, that the forego- ing  expectations  about  OID  could  change  because  of  differences  (1)  between  anticipated purchase prices and actual purchase prices or (2) between the assumed characteristics of the Trust Assets and the characteristics of the Trust Assets actually delivered to the Trust. The prepayment assumption that should be used in determining the rates of accrual of OID, if any, on the Regular Securities (as described in "Yield, Maturity and Prepayment Considerations" in this Supplement) is as follows: Group PSA 1 270% 2 250% In the case of the Classes FA, FB and FC, the constant value of LIBOR to be used for these determinations  is  5.2375%.  No  representation  is  made,  however,  about  the  rate  at  which prepayments on the Mortgage Loans underlying any Group of Trust Assets actually will occur or the level of LIBOR at any time after the date of this Supplement. See "Certain Federal Income Tax Consequences" in the Base Offering Circular. The  Regular  Securities  generally  will  be  treated  as  "regular  interests"  in  a  REMIC  for domestic building and loan associations and "real estate assets" for real estate investment trusts ("REITs") as described in "Certain Federal Income Tax Consequences" in the Base Offering Circular. Similarly, interest on the Regular Securities will be considered "interest on obliga- tions secured by mortgages on real property" for REITs. Residual Securities The Class RR Securities will represent the beneficial ownership of the Residual Interest in the Pooling REMIC and the beneficial ownership of the Residual Interest in the Issuing REMIC. The Residual Securities, i.e., the Class  RR Securities, generally will be treated as "residual interests" in a REMIC for domestic building and loan associations and as "real estate assets" for REITs,  as  described  in  "Certain  Federal  Income  Tax  Consequences"  in  the  Base  Offering Circular, but will not be treated as debt for federal income tax purposes. Instead, the Holders of the Residual Securities will be required to report, and will be taxed on, their pro rata shares of the taxable income or loss of the Trust REMICs, and these requirements will continue until there  are  no  outstanding  regular  interests  in  the  respective  Trust  REMICs.  Thus,  Residual Holders will have taxable income attributable to the Residual Securities even though they will not receive principal or interest distributions with respect to the Residual Securities, which could result in a negative after-tax return for the Residual Holders. Even though the Holders of the Class RR Securities are not entitled to any stated principal or interest payments on the Class RR Securities, the Trust REMICs may have substantial taxable income in certain periods, and offsetting tax losses may not occur until much later periods. Accordingly, a Holder of the Class RR Securities may experience substantial adverse tax timing consequences. Prospective S-51