Which of the following is not an internal control activity for cash?

a$.$ The functions of cash record keeping and cash custody are combined.

b$.$ Over$-$the$-$counter sales are processed with a cash register.

c$.$ The bank deposit receipt is returned to the Accounting Department where it is compared to the total amount that should have been deposited.

d$.$ For a cash payment, a voucher is prepared after all necessary supporting documents have been received.