A retailer offers refrigerators in 48 monthly installments in arrears of $6,500 each with an interest rate of 21.6% per annum with monthly capitalization. If a customer decides to buy a refrigerator in this way, but also decides to increase the payment at the end of each semester to $15,500, taking advantage of his Christmas bonus and semi-annual bonuses.

A) How long will it take the customer to finish paying for the refrigerator, considering that the first of these payments is made on the day of purchase?

B) How much will the customer pay in interest?