二層指数債券のモーゲージ証券

最近モーゲージ証券の利子分配を学んでいます。しかし二層指数債権の元本の計算方法がわかりにくいです。ファボジ氏の本によるとフローターの利子の金額をttibの固定利率に割る。however, it seems that the TTIB's face would then float, as this amount would be paid to the floater as interest only when the Libor rate is 0. It is unclear basically why the ttib interest amount is correlated to the floater's minimum interest. Using a different approach, the strike of the inverse floater, 7%, can be considered. Then all of the 6000000 in interest cash flow is split between the floater and the ttib. Then the floater interest of Libot plus 50bps on 75000000 is 5625000, and the remaining amount for the ttib is 375000. Dividing this by 13% results in 2884615.38, or the principal in the text. As Libor varies below 7%, the 375000 paid to the ttib remains constant, and the interest amount left over from the (変動する) floater and the (固定) ttib is paid to the inverse floater (as a percentage of 25000000-2884615.38 notional).