Answer:
The answer is: Establish a control system (checks and balances)
Step-by-step explanation:
Mary was in charge of all the operations regarding the use of cash in the company. The problem was that there was no one to control her work. If she prepared all the cash receipts and disbursements, she shouldn´t have been responsible for collecting the cash and matching them with the receipts she prepared herself.
The manager, Susan Lowe, couldn´t tell if cash was missing if Mary did the receipts and then matched the cash records for them. There was no way she could have checked if the amounts were correct. Peter should have been involved in this process, either by preparing the receipts or handling the cash and matching the records. That way the could have established some control system.