Two features of internal control are presented in the following sections. Each is followed by a list of four irregularitie that occurred in processing data. Identify the one irregularity from each list that would be discovered or prevented by the feature of internal control described. (a) The sum of the balances of the customer accounts in the accounts receivable subsidiary ledger is compared at the end of each month with the balance of the accounts receivable account in the general ledger by a person who has no responsibility for maintaining either the general ledger or the accounts receivable subsidiary ledger. (1) Five hours of services were rendered but the customer was only billed for 4 hours. (2) A cash receipt of $750 was recorded correctly in the accounts receivable controlling account but was posted to the customer's ledger as $75. (3) A bill for services rendered to Cole Co. was erroneously posted to the account of Coleman Co. (4) No entry was made in the accounting records for services rendered to a customer. (b) Both cash and credit charges for services rendered are recorded on prenumbered invoices. At the end of the day, all invoices are accounted for before the duplicate copies of the invoices are routed to the Accounting Department for entry into the accounts and the cash is sent to the Cashier's Department for deposit. (1) Some charge customers complained that the monthly statements of account did not add all amounts correctly. (2) Some clerks used incorrect hourly rates in preparing invoices. (3) Some clerks destroyed duplicate copies of cash invoices and misappropriated the cash. (4) Some charge customers complained that their monthly statements of account did not indicate credits for payments made