Why Coupon Rate on cash interest payment is taken differently on some questions?

Dear Sir,

Hope you are doing well.

I have created this account only to ask this question as I have been struggling over past few days on one issue. I know for redeemable bonds cash interest payments, we have to take coupon rate with par/nominal/book value given in the question unless if not stated then we assume 100 as par value. But I have seen some questions use 100 as par value although nominal is given in the Q. I am so confused. Please kindly help me?

for e.g
A company has 13% redeemable loan notes with a nominal
value of $7 million, trading at $105. They are due to be redeemed at
nominal value in five years’ time.
If the rate of corporation tax is 33%, what is the company’s
WACC?
Answer
Interest payment
(13 × (1– 0.33)) = 8.71

Why they didn’t multiply 13% with 7 million here even nominal value is given here in Question.
whereas in other question I don’t remember the details, but it was as follows:-
Debt 10% loan stock 20Y3 $80m Book value and market value $85m and while calculating IRR instead of taking 10% * 100 * (1-0.3) , they took 10% * 80m * (1-0.3), why?