The APR is 18.6%. This means that every month, 18.6 ÷ 12 = 1.55%
We can solve the total cost with a simple amortization:
Balance after Month 1: 1920.96 * 1.0155 = 1950.74
Payment of 720 reduces the balance to 1230.74
Balance after Month 2: 1230.74 * 1.0155 = 1249.81
Payment of 720 reduces the balance to 529.81
Balance after Month 3: 529.81 * 1.0155 = 538.02
Payment of 538.02 settle the payment.
Newton paid 720 in month 1, 720 in month 2, and settled the debt in month 3 with a payment of 538.02
His total payment is 720 + 720 + 538.02 = 1978.02
