Public projects of sixty thousand dollars ($60,000) or less may be performed by the employees of a public agency by force account, by negotiated contract, or by purchase order. (b) Public projects of two hundred thousand dollars ($200,000) or less may be let to contract by informal procedures. (c) Public projects of more than two hundred thousand dollars ($200,000) shall be let to contract by formal bidding procedure. (d) If all bids received are in excess of two hundred thousand dollars ($200,000), the governing body of the public agency may, by adoption of a resolution by a four-fifths vote, award the contract, at two hundred twelve thousand five hundred dollars ($212,500) or less, to the lowest responsible bidder, if it determines the cost estimate of the public agency was reasonable.