Based on the following information to answer questions from 39 to 40:
A mortgage-backed security has been divided into three classes or tranches as follows:
Tranche Ⅰ receives net interest and all the principal payments until it is completely paid off.
Tranche Ⅱ receives its share of net interest and starts receiving all the principal repayments after
Tranche Ⅰ has been completely paid off. Prior to that, it only receives interest payments.
Tranche Ⅲ receives monthly net interest and starts receiving all principal repayments after
Tranches Ⅰ and Ⅱ have been completely paid off. Prior to that, it only receives interest payments. For a relatively small decline in mortgage interest rates, which of the tranches has the least amount of prepayment risk