A corporation has asked you to prepare some multiple regression equations to estimate the effect of variables on fuel economy. The data for this study are shown below, and the dependent variable is miles per gallon. Complete parts a and b. Miles 43.2 37 32.2 39.1 37 19.8 19.5 20.6 19.3 20.5 Horsepower 50 67 49 73 61 108 140 137 105 98 Weight 1995 1900 1990 2080 1890 3375 3780 3580 3165 2725 a. Prepare a regression equation that uses vehicle horsepower and vehicle weight as independent variables. Let x, be defined as horsepower and X2 be defined as weight. y = ( 59.5288 ) +( 0.0209 )X, +( -0.0123 )X2 (Round to four decimal places as needed.) Interpret the coefficients. For a fixed weight , a 1-unit increase in horsepower leads to an expected increase of approximately 0.021 miles per gallon. b. Prepare a second biased regression with vehicle weight not included. (Round to four decimal places as needed.)