A company received $18,000 from a customer on December 1, 20X1 for future work to be performed and recorded the receipt of cash and the liability to complete the work (credit to unearned revenue). As of the year ended December 31, 20X1, two-thirds of the work has been completed. Record the necessary adjusting journal entry. DEBIT: Unearned Revenue for $6,000; CREDIT: Revenue for $6,000 DEBIT: Unearned Revenue for $12,000; CREDIT: Revenue for $12,000 DEBIT: Revenue for $6,000; CREDIT: Unearned Revenue for $6,000 DEBIT: Revenue for $12,000; CREDIT: Unearned Revenue for $12,000