Coupons are the rates x par, because the floating bond is reset at every payment date.
So with backward induction based on your tree you start with 105 105 and 103.9404. You discount these with the interest rates (untouched when you use them for discounting. And you go on like this. Rates at node 1 are less than the cap so you don’t need to modify them further.
I got an e-mail from Wanda at CFA Institute today. She said that her investigator checked and it’s correct as written.
So . . . I looked at the curriculum and, sure enough, the author of reading 37 says right up front that the term “set in arrears” means that the the rate is set at the beginning of the period and paid at the end.
Of course, this contradicts both other readings (swaps, for example) and common usage: the proper description is set in advance, _ paid _ in arrears.
I suggested that they ask the author to change his term to conform to common usage. We’ll see, but I’m not hopeful.
When you calculate the coupon you take into account the cap, i.e. if the interest rate is higher than the cap you use the cap, if it’s lower than the cap you use the interest rate.
For discounting to t-1 you use the interest rate unchanged, because it is the prevailing interest rate so for PV calculation you do not modify it.