Annual Compounded Interest in Amortization - Please Help!

Hi There, this is my first post. I am taking a business mathematics course, and the present focus is on amoritization. Thus far I have not run into any major problems, but one has now come along: Compounding annually.

Let me clarify the question, and I'll let you know what I've done so far:

Greg and Terri have just bought a home, mortgaged for $90,000, which is being amortized over twenty years with monthly payments. If the mortage has an interest rate of 23.21 percent, compounded annually, find:

a) The monthly payments.

b) the amount outstanding after the 24th payment.

c) construct a partial amortization table to show the first two payments and the last two payments of the loan.

a) This part I think I did correctly. I'm not sure how to type the formula, but because it was compounded annually, I used "f" where f= (1+i) to the power of c - 1. My answer was a monthly payment of $1603.79.

b) This has completely thrown me for a loop! I understand this process based off a monthly or semi-annual compound period, but I have no idea how to proceed with annual compounding. My textbook only uses monthly, quarterly, semi-annual.

Thank you so much for your help!