The cost of a used car is highly correlated with the following variables: age of the car V= volume of engine D = number of doors A = accessories and style lSt 5 (years) 1000 V-2500 (cubic centimeters) D = 2, 3, 4, 5 = 1, 2, 3, 4, 5, 6 (qualitative) Using regression analysis, the following relationship between the cost of a car and the four independent variables was found: purchase cost-6-1)-84 1+-k vx (a) Plot the purchase cost as a function of each variable (assume all other variables are held constant). (b) From the plots, which variable has the largest effect on cost? (c) If you have a $5,000. List the different types of cars (combinations of the parameters) that you can afford