Please explain step by step how to solve

You are the loan department supervisor for a bank. This installment loan is being paid off early, and it is your task to calculate the rebate fraction, the finance charge rebate (in $), and the payoff for the loan (in $). (Round dollars to the nearest cent.) Amount Financed Number of Payments Monthly Payment Payments Made Rebate Fraction Finance Charge Rebate Loan Payoff $1,800 18 $127.89 14 $ $