Base Offering Circular – Multifamily 12 If at any time after the applicable Treasury Index becomes unavailable it again becomes available, the Interest Rates for the related Treasury Index Classes for each subsequent Accrual Period will be calculated by reference to the applicable Treasury Index. Determination of the Prime Rate Unless otherwise provided in the applicable Offering Circular Supplement, on each Floating Rate Adjustment Date, the Trustee (or its agent) will calculate the Interest Rates of Prime Rate Classes for the next Accrual Period by reference to the rate published as the “Prime Rate” in the “Money Rates” section or other comparable section of The Wall Street Journal on that Floating Rate Adjustment Date.  If The Wall Street Journal publishes a prime rate range, then the average of that range, as determined by the Trustee, will be the Prime Rate. In the event The Wall Street Journal no longer publishes a “Prime Rate” entry, the Trustee (or its agent) will designate a new methodology for determining the Prime Rate based on comparable data. The Trustee (or its agent) will select a particular methodology as the alternative methodology only if it receives an Opinion of Counsel that the selection of that methodology will not cause the related Trust REMIC or Trust REMICs to lose their status as REMICs for federal income tax purposes. If at any time after the Prime Rate becomes unavailable in The Wall Street Journal it again becomes available, the Trustee will calculate the Interest Rates for the Prime Rate Classes for each subsequent Accrual Period by reference to the Prime Rate published in The Wall Street Journal. Modification and Exchange General Certain Series will provide for the issuance of one or more Classes of MX Securities.  In any such Series, subject to the rules, regulations and procedures of the Book-Entry Depository, all or a portion of a specified Class or Classes of REMIC Securities will be delivered to a grantor trust that will issue Modifiable Securities that represent beneficial ownership of those REMIC Securities.  All or a portion of the interests in such REMIC Securities may be exchanged for a proportionate interest in one or more related MX Classes, as provided in the applicable Offering Circular Supplement.  Similarly, all or a portion of the related MX Class or Classes may be exchanged for proportionate interests in the related Class or Classes of REMIC Securities and, if so provided, in other related MX Classes.  This process may occur repeatedly.  For this purpose, “related” Classes are those within the same “Combination” shown in the Available Combinations Schedule in the applicable Offering Circular Supplement. Each MX Security issued in an exchange will represent a beneficial ownership interest in, and will be entitled to receive a proportionate share of the distributions on, the related REMIC Securities (or the related MX Securities), and the Beneficial Owners of the MX Classes will be treated as the Beneficial Owners of proportionate interests in the related Class or Classes of REMIC Securities (or the related MX Securities). In each Series that includes MX Securities, the Classes of REMIC Securities identified in the applicable Offering Circular Supplement will initially be issued.  Certain of those Classes