The Purchasing Agent shall certify to the correctness of all bills incurred by the Purchasing Department in the following manner:
(a) that the material, supplies, equipment or contractual services were received;
(b) that the quality of materials, supplies, etc., were in accordance with the specifications or purchase order; (c) that all prices charged are fair;
(d) that a purchase order has been issued for materials, supplies, equipment or contractual services.
The above mentioned procedure must be complied with before invoices are forwarded for payment by the Controller.