A Present and Future Value Math Problem! Help!?

So I have this problem and it keeps on telling me I have the wrong answer. Someone help.

Mr. Smith is purchasing a $100000 house. The down payment is 20% of the price of the house.
He is given the choice of two mortgages:

A) a 20-year mortgage at a rate of 8% compounded monthly.
Find:
(i) The monthly payment:
(ii) The total amount of interest paid

(B) a 15-year mortgage at a rate of 8% compounded monthly.
Find:
(i) The monthly payment
(ii) The total amount of interest paid