Ron did not pay his credit card bill in full last month. He wants to pay it in full this month. On this month's bill, there is a mistake in the average daily balance. The credit card company lists the average daily balance on his bill as $510.50. Ron computed it himself and found that it is $410.50.
a. The APR is 18%. What finance charge did the credit card company compute on Ron's bill?
b. If Ron's average daily balance is correct, what should the finance charge be?