At the end of the current year, $17,600 of fees have been earned but have not been

Question:

At the end of the current year, $17,600 of fees have been earned but have not been billed to clients.
a. Journalize the adjusting entry to record the accrued fees.
b. If the cash basis rather than the accrual basis had been used, would an adjusting entry have been necessary? Explain.