(1) The following commodities may be purchased without soliciting bids: Commodities in instances of an unforeseen and unavoidable emergency.
(2) Provided, no emergency purchase shall be approved by the superintendent unless a statement in writing shall be attached to the purchase order describing the emergency necessitating the purchase of the commodity without competitive bidding;
(3) Commodities available only from the United States government;
(4) Utility services, the rates for which are subject to regulation by a state agency or a federal regulatory agency;
(5) With the exception of used school buses, used equipment and machinery; and
(6) Commodities available only from a single source.
(7) However, the purchasing official must determine in writing that it is not practicable to use other than the required or designated commodity or service, and a copy of this statement shall be attached to the purchase order.