dirk ward borrowed 12000 for investment purposes on May 21 on a demand note providing a variable rate of interest and payment of any accrued interest in December 31. he paid 1000 on June 21, 100 on September 22 and 500 on November 18. how much is the accursed interest on December 31 if the rate of interest was 8% on May 21 8.25 effective August 1 and 8.65 effective November 1?