Mainland Supply Company recently changed its system of internal control over cash disbursements. The system includes the following features. Instead of being unnumbered and manually prepared, all checks must now be prenumbered and written by using the new checkwriting machine purchased by the company. Before a check can be issued, each invoice must have the approval of Erin McGarry, the purchasing agent, and Barb Speas, the receiving department supervisor. Checks must be signed by either Amaika Blake, the treasurer, or Ken Yost, the assistant treasurer. Before signing a check, the signer is expected to compare the amount of the check with the amount on the invoice.
After signing a check, the signer stamps the invoice PAID and inserts within the stamp, the date, check number, and amount of the check. The "paid" invoice is then sent to the accounting department for recording.
Blank checks are stored in a safe in the treasurer's office. The combination to the safe is known only by the treasurer and assistant treasurer. Each month, the bank statement is reconciled with the bank balance per books by the assistant chief accountant. All employees who handle or account for cash are bonded.

Instructions
Identify the internal control principles and their application to cash disbursements of Mainland Supply Company.