Mel's Photography borrowed $15 000 on March 10 on a demand note. The loan was repaid by payments of $4000 on June 20, $3000 on September 1, and the balance on November 15. Interest, calculated on the daily balance and charged to Mel's Photography current account on the last day of each month, was at 5.5% on March 10 but was charged to 6.25% effective June 1 and to 6% effective October 1. How much did the loan cost?