The bridgeport water department has a monthly service charge of $12.90 and a usage charge of $1.57 for every 100 cubic feet of water. which of the following equations can be used to determine the monthly water bill of a bridgeport resident? (let x represent the amount of water used in hundreds of cubic feet and y represent the monthly cost.) a. y = 1.57x + 12.90 b. y = 1.57x - 12.90 c. y = 14.47x d. y = 0.0157x + 12.90