The following shall apply to bids.
1. Written bids. Bids shall be in writing, sealed with outside envelope or wrapper plainly marked "Bid, not to be opened until (with appropriate date inserted)," and mailed to or filed with the superintendent of the unit.
2. Time of opening. A director or employee of the school administrative district may not open a bid until the appointed time.
3. Public opening. At the time and place stated in the public notice, and open to the public, all bids shall be opened by the superintendent or, in the superintendent's absence or disability, by any director designated for the purpose by the chairman of the board of directors.
4. Reading. If any citizens who are not school administrative district directors or employees, or if any representatives of the press are present, bids shall at the time either be made available for examination by them or shall be read aloud in a manner to be heard plainly by those in attendance.
5. Exceptions.