STUFF IN CFAI BUT NOT IN SCHWESER thread, especially, elsewhere, perfect

former

I know this thread may be a bit redundant, but figured it would be good to give it a fresh start with two weeks left.
This is for any topics or formulas you come across in CFAI (especially the EOC!!!), but didn’t see in Schweser. If you could specify CFAI Volume & Page #/Question#, that would be perfect. This could even apply to things you did read about in Schweser, but still failed to give you enough info to answer questions in the CFAI text (or elsewhere).
#1. Mortgage Backed Sector of the Bond Market - Calculating Notional Amount of Interest Only Strip on an MBS (Page 382-383, CFAI Vol 5)
Notional Amount of an I.O. strip at x%
= {Original Tranche Par Value * Excess Interest %} / {x%}
where Excess Interest % = Collateral Tranche’s Coupon Rate - Tranche Coupon Rate
Note: Both Excess Interest and x% should be input as DECIMALS.
This came up in CFAI EOC #28, page 412.
PS There is content on Floating rate tranches (pg 380) and associated EOC questions, but too lazy to go over that right now…if anyone wants to give it a shot, please do