Which one of the following would not be considered a substantive audit procedure?
A. Obtaining a letter from an investment broker confirming an account balance.
B. Using generalized audit software to identify all accounts receivable over 90 days outstanding.
C. Selecting a sample of sales orders and checking that all orders are authorized by a sales manager.
D. Multiplying the number of employees on each pay scale by the yearly pay rate to determine an estimate of payroll expense.