
Answer:
a) For the amount earned and billed,
Debit Unearned fees  $39,750
Credit Service revenue  $39,750
b)To recognize the accrued or unbilled revenue that has been earned,
Debit Unbilled receivable  $24,650
Credit Service revenue    $24,650
Explanation:
When fees are collected in advance, the entries required are a debit to cash account and  a credit to unearned fees.
As the revenue is earned through the performance of the service, the entries required are debit to unearned fees and a credit to service fee.
When revenue is earned but unbilled, the entries required are
Debit Unbilled receivable
Credit Service revenue