Southern Airlines received payment from a customer on December 1, 2020, for a round trip airline ticket from Toronto to Orlando in the amount of $500. The flight from Toronto to Orlando occurs on December 23, 2020, and the return flight to Toronto is on January 11, 2021. Which of the following is included in the adjusting entry needed on December 31, 2020, to record earned revenue from this transaction? O O O O Debit to Unearned Revenue, $250. Debit to Unearned Revenue, $500. Credit to Unearned Revenue, $500. Credit to Unearned Revenue, $250