Bid documents will clearly indicate that the purchaser has the right to reject any or all bids, waive informalities or irregularities with respect thereto, and to contract in the best interest of the district. The following is a list of formalities which will not be waived:

(1) Bids received after the bid opening date and time indicated on the bid document will be returned to the bidder unopened. Bids postmarked prior to bid opening time, but not received, will not be considered. Telephoned or telegraphed bids and alterations, except for unconditional withdrawals, will not be considered unless authorized in the bid terms and conditions.

(2) Bids received that have not been signed by an authorized agent.

(3) Bid bonds, if required, not included with the bid.