Answer:
a. add $45 to the book's balance
Step-by-step explanation:
In a situation where a check which was correctly written and as well paid by the bank for the amount of $638 was incorrectly recorded as the amount of $683 on the company's books which means that the appropriate treatment on the bank reconciliation statement would be to add the amount of $45 ( $683-$638) to the book's balance.