(Annuity payments) Calvin Johnson has a $5,500 debt balance on his Visa card that charges 13.6 percent APR compounded monthly. In 2009, Calvin's minimum monthly payment is 4 percent of his debt balance, which is $220. How many months (round up) will it take Calvin Johnson to pay off his credit card if he pays the current minimum payment of $220 at the end of each month? In 2010, as the result of a federal mandate, the minimum monthly payment on credit cards rose to 5 percent. If Calvin made monthly payments of $275 at the end of each month, how long would it take to pay off his credit card? a. If Calvin made monthly payments of $220 at the end of each month, how long would it take to pay off his credit card? months (Round up to the nearest unit.) b. If Calvin made monthly payments of $275 at the end of each month, how long would it take to pay off his credit card? months (Round up to the nearest unit.)