That (a) proposals for the construction of an improvement shall be solicited as sealed competitive bids after public advertisement at least once in a newspaper having general circulation in the municipality not less than 10 days prior to the date set for receipt of bids. Upon or after the acceptance by the governing body of a bid, or combination of bids, the governing body may determine the principal amount of bonds to be issued for the proposed improvement, taking into account the amount of the accepted bid or bids, and all other costs of the improvement. Each contract shall be supported by a performance bond for the full amount thereof, with good surety to be approved by the governing body. A bid shall not be binding on a contractor unless the governing body awards a contract within 90 days after the date of opening bids. (b) If the governing body determines that no bids are acceptable, it may direct that the improvement be accomplished by the municipality's own forces, in which event the costs of construction included in the total costs for purposes of determining improvement assessments shall not exceed the lowest construction bid or bids which conform to all bid requirements. [As added by Priv. Acts 1970, ch. 276, § 5]