Damian has a balance of $10,200 on his credit card. He threw the card away so he can never use it again. He has 3 1/2 years to pay off the balance. The interest rate on his card is 21%.

a. At the end of the 3 1/2 years, how much interest has he paid? ________
b. When Damian pays off his credit card, how much will he have paid in all? _____