infinite math
posted by tommy .
Hey guys! really need help with this one!!!
On December 31, 1995, a house is purchased with the buyer taking out a 30year $90,000 mortgage at 9% interest compounded monthly. The mortgage payments are made at the end of each month. Calculate:
(A) the unpaid balance of the loan on December 31,2005, just after the 120th payment.
(B) the interest that will be paid during January 2006.
Thanks in advance!

first you need the monthly payment
PV = 90000
i = .09/12 = .0075
n = 12x30 = 360
90000 = Payment [ 1  1.0075^360]/.0075
payment = 724.16
balance right after 120th payment
= 90000(1.0075)^120  724.16( 1.0075^120  1)/.0075
= 80486.77
interest on next month = 80486.77(.0075) = 603.65