On January 1 of the current year, the Barton Corporation issued 8% bonds with a face value of $83,000. The bonds are sold for $80,510. The bonds pay interest semiannually on June 30 and December 31 and the maturity date is December 31, five years from now. Barton records straight-line amortization of the bond discount. The bond interest expense for the year ended December 31 is Oa. $6,640 Ob. $2,490 Oc. $553 Od. $7,138