The general manager of QuickFix, a chain of quick-service, no-appointment auto repair shops, wants to develop a model to forecast monthly vehicles served at any particular shop based on four factors: garage bays, population within 5-mile radius, interstate highway access (1 = convenient access, 0 = otherwise), and time of year (1 = winter, 0 = otherwise). He believes that, all else equal, shops near an interstate will service more vehicles and that more vehicles will be serviced in the winter due to battery and tire issues. A sample of19 locations has been obtained. A portion of the data isshown in the accompanying table.

a. Estimate the regression equation relating vehicles serviced to the four explanatory variables.
b. Interpret each of the slope coefficients.
c. At the 5% significance level, are the explanatory variables jointly significant? Are they individually significant? What about at the 10% significance level?
d. What proportion of the variability in vehicles served is explained by the four explanatory variables?
e. Predict vehicles serviced in July for a particular location with 5 garage bays, a population of 40,000, and convenient interstate access.

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Vehicles Served (per month) 200 351 Population in 5-Mile Radius (000's) 15 Interstate Access? Time of Year? Garage Bays 464 74