Answer: revenue of $10,000 in 2017
Step-by-step explanation:
Accrual basis of accounting is a method that is used in accounting whereby the revenue or expenses have to be recorded when the transaction is made and not when the payment dor the transaction is made or received.
Since we are told that Costello Company performs work for a customer and bills the customer $10,000 in 2017, therefore if Costello uses the accrual-basis of accounting, then Costello will report revenue of $10,000 in 2017.