The electric power consumed each month by a chemical plant is thought to be related to the average ambient temperature x1, the number of days in the month x2, the average product purity x3, and the tons of product produced x4. The past year's historical data are available and are presented in the following table.

(a) Fit a multiple linear regression model using the above data set.

(b) Predict power consumption for a month in which x1 = 75°F, x2 = 24 days, x3 = 90%, and x4 = 98tons

24 240 25 91 100 31 45 60 65 72 80 84 75 60 50 90 88 87 91 95 236 290 21 24 25 25 110 274 301 316 88 94 99 97 96 110 105 94 87 26 25 25 24 25 25 23 300 296 267 276 86 88 91 90 89 288 261 100 38 98