Use PMT =[1(1+nr)nt]P(nr) to determine the regular payment amount, rounded to the nearest dollar. Your credit card has a balance of $4200 and an annual interest rate of 16%. You decide to pay off the balance over four years. If there are no further purchases charged to the card, a. How much must you pay each month? b. How much total interest will you pay? a. The monthly payments are approximately $ (Do not round until the final answer. Then round to the nearest dollar as needed.) b. The total interest paid over 4 years is approximately $ (Round to the nearest dollar as needed.)