On January 1, 2017, Kepler Corporation, issued $5,000,000 of 10-year, 8% convertible debentures at 102. Interest is to be paid semiannually on June 30 and December 31. Each $1,000 debenture can be converted into five shares of Derrick Corporation $100 par value common stock after December 31, 2018. On January 1, 2019, $500,000 of debenture are converted into common stock, which is then selling at $120. An additional $500,000 of debenture are converted on March 31, 2019. The market price of the common stock is then $110. Accued interest at March 31 will be paid on the next interest date Bond premium is amortized on a straight-line basis. The account balance of unamortized bonds as of March 31, 2019 is for the amount of:

a. $72,000 b. $108,000 c. $64,250 d. $64,000