On September 1, Knowledgeable Company began a contract to provide services to Guidance Required Company for six months, with the total $64,800 payment to be made at the end of the six-month period. Equal services are provided each month. The firm uses the account Fees Receivable to reflect amounts due but not yet billed. What proper adjusting entry would Knowledgeable Company make on December 31, the end of the accounting period (no previous adjustment has been made)? Select one: O A. Fees Receivable Service Fees Earned Unearned Service Fees 64,800 43,200 21,600 OB. Fees Receivable Service Fees Earned 43,200 43,200 OC. Cash 43,200 Service Fees Earned 43,200 o D. Unearned Service Fees Service Fees Earned 43,200 43,200