On January 1, Frank Jensen bought a used car for $7200 and agreed to pay for it as follows: 1/3 down payment; the balance to be paid in 36 equal monthly payments; the first payment due February 1; an annual interest rate of 9%, compounded monthly.

Note: Use a interest rate of 0.75% per month (which corresponds to an annual nominal interest rate of 9% as given in the problem).

a) What is the amount of Frank's monthly payment? (I got $76.34 using A =P[i(i+1)^N]/(i+1)^N-1)

b). During the summer, Frank made enough money to pay off the entire balance due on the car as of October 1. How much did Frank owe on October 1?