If tucson's average rainfall is 12 1/4 and yumas is 2 3/5 inches, how much more rain, on an average does tucson get?

Suppose that a households monthly water bill (in dollars) is a linear function of the amount of water the household uses (in hundreds of cubic feet, hcf). when graphed, the function gives a line with slope of 1.65. if the monthly cost for 13 hcf is $46.10 what is the monthly cost for 19 hcf?