Question 1172840
You got a negative number, so that is the first hint something is incorrect. rate per month is 0.01 or 1%, 12%/12. 
a divided by (1+r)^n-1/r(1+r)^n
n=36 payments and r is int. rate/12, for 12 payments per year.
a=$13000
the denominator is (1.01^36-1)/0.01(1.01)^36=0.431/0.143=30.107.
13000/30.107=$431.79.  Note: round at the end; carry all intermediate calculations to the final one.