(a) The purchasing agent shall have the power and it shall be his duty to purchase or contract for supplies and contractual services needed by any using agency of the city and sell surplus personal property of such using agencies, in accordance with the ordinances of the city and such rules and regulations as shall be prescribed by the Mayor and approved by the Council.
(b) The purchasing agent shall have the authority to join with other units of government in a cooperative purchasing venture when the best interests of the city would be served.