Suppose the Chans in Exercise 16 use a credit card rather than an installment plan. Assume that they make the same down payment, have no finance charge the first month, make no additional purchases on their credit card, and pay $432 per month plus the finance charge starting with the second month. The interest rate is 1.3% per month.

(a) How many months will it take them to repay the loan? 

(b) How much interest will they pay on the loan?

(c) Which method of borrowing will cost the Chans the least amount of interest, the installment loan in Exercise 16 or using the credit card?

Reference Exercise 16:

Mr. and Mrs. Chan want to buy furniture that has a cash price of $3450. On the installment plan, they must pay 25% of the cash price as a down payment and make six monthly payments of $437.