On may 1, sellers marketing company received $1,500 from franco marcelli for a marketing campaign effective from may 1 this year to april 30 of the following year. the cash receipt was recorded as unearned fees and at year-end on december 31, $1,000 of the fees had been earned. assuming adjustments are only made at year-end, the adjusting entry on december 31 would be: a) a debit to fees earned and a credit to cash for $1,000. b) a debit to fees earned and a credit to cash for $500. c) a debit to unearned fees and a credit to cash for $500. d) a debit to fees earned and a credit to unearned fees for $500. e) a debit to unearned fees and a credit to fees earned for $1,000.