Hello. Please keep in mind this is a multi-part question. Thank you in advance for your help.

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(Annuity payments) Calvin Johnson has a $4,000 debt balance on his Visa card that charges 10.5 percent APR compounded monthly. In 2009 , Calvin's minimum monthly payment is 3 percent of his debt balance, which is $120. How many months (round up) will it take Calvin Johnson to pay off his credit card if he pays the current minimum payment of $120 at the end of each month? In 2010 , as the result of a federal mandate, the minimum monthly payment on credit cards rose to 4 percent. If Calvin made monthly payments of $160 at the end of each month, how long would it take to pay off his credit card