Which, if any, of the followingsituations represent improper segregationof functions? Explain your answer. a. The billing deparment prepares the customers' invoices and records the sale in the sales journal. b. Mail room clerk opens cash receipts envelopes from customers and also prepares the remittance list. c. Accounting clerk receives journal vouchers from various departments and also posts to the GL accounts. d. The sales department approves sales credit memos as the result of product returns and forwards these to the AR department, which adjusts the customer accounts to reflect the return