7-3-1323. Competitive, advertised bidding required for certain contracts. All contracts entered into by the municipality for supplies or materials, for any public work, or for the construction, reconstruction, repair, maintenance, or operation of any public works or improvements, for which must be paid a sum exceeding $2,000, shall be awarded to the lowest responsible bidder after public advertisement and competition as may be prescribed by ordinance, but the manager shall have the right to reject all bids and advertise again. All advertisements as to contracts shall contain a reservation of the foregoing right. All contracts entered into by the municipality shall be signed by the manager after approval thereof by the commission.