To arrive at an accurate balance on a bank reconciliation statement, a credit memorandum from the bank for the collection of a note and interest should be

Must be added to the book balance.

Explanation:

The correct treatment would be to add this value to book balance because the bank has increased our bank balance by the note and interest amount. This must be accounted for as increase in the book balance because we have borrowed money and also that yearly interest income was also added to our bank checking account.

Hence it must be added to cash book balance in order to reconcile with the bank balance.