Cellulon, a manufacturer of home insulation, wants to develop guidelines for builders and consumers on how the thickness of the insulation in the attic of a home and the outdoor temperature affect natural gas consumption. In the laboratory, it varied the insulation thickness and temperature. A few of the findings are:

Monthly Natural Gas Consumption (cubic feet), Y	Thickness of Insulation (inches), X1	Outdoor Temperature (F), X2
30.3		5		50
28.8		12		40
23.8		8		49

On the basis of the sample results, the regression equation is:

= 133.23 2.76X₁ 1.78X₂

a.	How much natural gas can homeowners expect to use per month if theyinstall5 inches of insulation and the outdoor temperature is 50 degrees F?(Round youranswerto 2 decimal places.)
	cubic feet

b.	What effect would installing 8 inches of insulation instead of 5 have on the monthly natural gas consumption (assuming the outdoor temperature remains at 50 degrees F)?(Round your answers to 2 decimal places.)
	A(Click to select)increasedecreaseofcubic feet monthly natural gas consumption, down tocubic feet.

c.	Why are the regression coefficientsb1andb2negative? Is this logical?

(Click to select)NoYes

, logically, as theamountof insulation

(Click to select)increasesdecreases

and outdoor temperature

(Click to select)increasesdecreases

, the consumption of natural gas

(Click to select)increasesdecreases

.