The successful bidder shall execute a bond to the city or town, in an amount equal to fifty percent (50%) of the entire contract price of the improvement, conditioned that the party shall well and truly perform all of the terms and conditions of the contract, in a good and workmanlike manner, and in accordance with the plans and specifications, which shall form part of the contract, and shall indemnify and hold the city harmless from all losses, costs, and expenses that it may sustain by reason of any negligence or default of such contractor.