Using My SQL, in the book Concepts of DBM 6th Edition using Premiere Products. When updating a customer, add the difference between the new balance and the old balance multiplied by the sales rep's commission rate to the commission for the corresponding sales rep. And When deleting a customer, subtract the balance multiplied by the sales rep's commission rate from the commission for the corresponding sales rep. The book doesn't really explain the triggers well enough to understand how to answer these two questions.