On April 1, 2010 your company finances partial payment of the sales of machinery to a customer for a 20,000, 3-year, 8% note receivable. Interest is payable annually on April 1. On December 31 2010, an adjusting entry debits Interest Receivable and credits Interest Revenue for 1,600. The entry necessary to correct the error before the books are closed would include....

a. a $400 debit to Interest Revenue

b. a $400 credit to Interest Expense

c. a $400 credit to Unearned Interest receivable

d. a $400 credit to sales