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 2015 model year. (Refer to Problem 29, Section 4.1.)

(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 Cadillac CTS weighs 3649 pounds and gets 20 miles per gallon. Is the miles per gallon of a CTS 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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Car Weight (Ib) Miles per Gallon 4724 Buick LaCrosse 17 Cadillac XTS 4006 18 Chevrolet Cruze 3097 22 Chevrolet Impala 3555 19 Chrysler 300 4029 19 Dodge Charger 3934 19 Dodge Dart 3242 24 2960 Ford Focus 26 Ford Mustang 3530 19 Lincoln MKZ 3823 18