Answer
(a) Error does not affect trial balance
(b) Error does affect trial balance
Work Step by Step
(a) The journal entry was recorded incorrectly for this transaction; however, it would not prevent the trial balance from balancing, since both the debit and credit amounts were $600.
(b) This transaction records the proper accounts, but not for the correct amounts. The error made in this transaction would prevent the trial balance from balancing, and it would be off by 720 dollars (800 - 80).