Amount of purchases=15,000. Down payment= 2,000. Rate of interest=8%. Term of loan=5 yrs. Monthly payment amount (P and I)=? Find the Monthly payment amount. the answer i got is 322.80.

I did the problem by A = 13000(1 + .08/12)^(12*5) = $19,367.99

Monthly payment = $322.80.

My friend said i did the problem wrong and she got $263.64 and wont explain how. I am so lost.

my other problem is like this

2.) Amount of purch.= 128,000. DP= 30,000. Rate of interest=5%. Term of loan is 30 years. What is the monthly payment amount (P. & I.)?

My answer came out to be A = 98000(1 + .05/12)^(12*30) = $437,838.94

Monthly payment = $1,216.22. wrong again?