All questions refer to data on average monthly sales of a (now extinct) chain of rental video stores. The data contains the following variables for each store in the sample : Sales are the average monthly sales (in thousands of dollars ), Population is the neighborhood population (in thousands ), Advertising is the annual advertising expenses (in dollars ), DVD Library is the number of DVDs in the library , and VHS Library is the number of VHS tapes in the library 1. Run a regression to determine how monthly sales are affected by all the other variables . Which of the following is the population model ? a) Sales = B .+ B , Advertising + B , DVD_Library + B, Population + B, VHS_Library + E E~ N(0, (03) 2) b) Sales = B. + 3, Advertising + B, DVD_Library + B; Population + 3, VHS_Library + 8 E~N (0, (432.484)2) c) Sales = -61.420 + 0.484Advertising + 1.349DVD_Library + 282.307 Population -0.408VHS_Library E ~N (0, (432.484)2) d) Sales -61.420 + 0.484Advertising + 1.349DVD_Library + 282.307 Population -0.408VHS_Library + E E~N (0, (432.484) 2)