Suppose that on January 1 you have a balance of $3900 on a credit card whose APR is 19%, which you want to pay off in 1 year. Assume that you make no additional charges to the card after January 1. a. Calculate your monthly payments. b. When the card is paid off, how much will you have paid since January 1? c. What percentage of your total payment from part (b) is interest? a. The monthly payment is $ (Do not round until the final answer. Then round to the nearest cent as needed.)