Let x be the size of a house (in square feet) and y be the amount of natural gas used (therms) during a specified period. Suppose that for a particular community, x and y are related according to the simple linear regression model with the following values. 3= slope of population regression line = 0.013 a = y intercept of population regression line = -7 Houses in this community range in size from 1,000 to 3,000 square feet. (a) What is the equation of the population regression line? y= (b) Graph the population regression line by first finding the point on the line corresponding to x = 1,000 and then the point corresponding to x = 2,000, and drawing a line through these points. y y y 2500 2000 1500 1000 O 500 10 20 30 40 40 30 20 10 y 500 1000 1500 2000 2500 2500 2000 1500 1000 500 80000 110000 140000 170000 40 30 20 10 DO 500 1000 1500 2000 X 2500