How to journalize this problem

A rental company owns a building from which it leases out multiple offices. During the year it received the following advance rental payments for one year leases from separate tenant; $24000 in June, $36000 in August, and $12000 in October , The leases started the first of the month following the payment. Assume that these are the only advance rental payments received and that no adjusting entries were made during the year. Find the balance of the unearned rent revenue account at year end on Dec 31 . Also find the amount of the adjustmend needed at year-end