$3$: The electric power consumed each month by a chemical plant is thought to be related to the average ambient temperature $($x$1),$ the number of days in the month $($x$2),$ the average product purity $($x$3),$ and the tons of product produced $($x$4).$ The past year$$s historical data are available and are presented in Table $3.$ Build regression models for the data using the following techniques:

a$)$ Forward selection.

b$)$ Backward elimination.

c$)$ Comment on the models obtained. Which model would you prefer?

MUST answer using excel. Please answer all, will upvote.