Answer:
$679.31 
Explanation:
The formula for the monthly payment (P) on a loan of A dollars that is paid back in equal monthly payments over n months, at an annual interest rate of i % is 

We must express the interest rate on a monthly basis. 
i = 8.3 %/yr = 0.6917 %/mo = 0.006 917 
A = $90 000 
n = 360 mo 




P = $679.31 
Heidi’s monthly payment is $679.31.