Which of the following controls would be least effective in ensuring that the correct product is shipped and billed at the approved price?

a. Self-checking digits are used on all product numbers, and customers must order from a catalog with product numbers.

b. The sales order taker verbally verifies both the product description and price with the customer before the order is closed for processing.

c. The sales order taker prepares batch totals of the number of items ordered and the total dollar amount for all items processed during a specified period of time

(e.g., | hour).

d. The product price table is restricted to the director of marketing, who alone can approve changes to the price file.