Joe Foss has worked for Dr Sam Milton for several years. Joe demonstrates a loyalty that is rare among employees. He hasn't taken a vacation in the last three years. One of Joe's primary duties at the medical office is to open the mail and list the checks received. He also takes cash from patients at the cashier window as patients leave. At times it is so hectic that Joe doesn't bother with giving each patient a receipt for the cash paid on their accounts. He assure them he will see it to it that they receive the proper credit. When the traffic is slow in the office Joe offers to help Ann and post the payments to the patient's account receivable. She is always happy to receive his help because he is a very considerate worker. Identify any principles of internal control that may be violated in this medical office situation