The activity on Charlie Wilson's Visa account for one billing period is shown below. Find the average daily balance and the finance charge if the billing period is November 11 through December 10, the previous balance was $643.49, and the annual interest rate is 20%.

November 15 payment $100.00

November 28 office supplies $28.73

December 1 toy store $316.65

the answer for average daily balance is NOT 438.82.

Thanks. In addition, I believe the office supplies and toy store amounts are charges, not income, but I am not 100% sure.