I am stuck on this for 1 hour now. I really need some help. ASAP, anyone please.

Dirk Ward borrowed $13,000.00 for investment purposes on May 5 on a demand note providing for a variable rate of interest and payment of any accrued interest on December 31. He paid $1000 on June 25, $100 on September 23, and $1200 on November 19. How much is the accrued interest on December 31 if the rate of interest was 8% on May 5,8.3% effective August 1 , and 8.6% effective November 1 ? The accrued interest on December 31 is $ (Round the final answer to the nearest cent as needed. Round all intermediate values to six decimal places as needed.)