An engineer wants to determine how the weight of a car, x, affects gas mileage, y. The following data represent the weights of various domestic cars and their miles per gallon in the city for the 2011 model year.

(a) Find the least-squares regression line treating weight as the explanatory variable and miles per gallon as the response variable.
(b) Interpret the slope and y-intercept, if appropriate.
(c) A Buick Regal weighs 3600 pounds and gets 18 miles per gallon. Is the miles per gallon of a Regal above average or below average for cars of this weight?
(d) Would it be reasonable to use the least-squares regression line to predict the miles per gallon of a Toyota Prius, a hybrid gas and electric car? Why or why not?

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Weight Miles pei Gallon, y 17 16 25 19 21 23 17 24 19 17 18 Car Buick Lucerne Cadllac CTS Chevrolet Cobalt Chevrolet Impala Chrysler Sebring Sedan Dodge Caliber Dodge Charger Ford Focus Ford Mustang Lincoln MKZ Mercury Sable (pounds), x 3735 3860 2721 3555 3319 2966 3727 2605 3473 3796 3310