Carl has a credit card with a balance of $5,260 and an apr of 21%. with the monthly payments he has been making, carl would be able to pay off his credit card in 18 months. after receiving a promotional offer in the mail, carl decides to transfer his balance to a new credit card with a 15% "introductory" apr for the first 12 months. after 12 months, the apr increases to 23%. how much will carl save in finance charges (interest) if he pays off the credit card before the introductory apr expires? a. $285.38 b. $480.30 c. $789.00 d. $917.42