John had Student Loans totalling $3800 when he completed her program at Columbia College in December. He had enough savings at the end of June to pay the interest that had accrued during the 6-month grace period. John made arrangements with his credit union to start end-of-month payments of $60 in July. He chose the fixed interest rate option (at prime plus 5%) when the prime rate was at 5.5%. a) Calculate the balance owed at the end of the grace period. b) Calculate the balance owed after the September 30 payment.

Pls include the formula so I can learn form it, thank you!