Answer:
Explanation:
In this situation , the order has been placed and executed . Cancelling the order is impossible . The execution of an order is the completion of a buy or sell order for a security ,hence it is irrevocable and biding on both the seller and the buyer and none of the two parties can cancel it at such time.
The best and appropriate procedure to handle the situation is to explain the procedures and guiding rules in buying stock to the customer and make him to realize that the order has been executed and biding on them.