A supermarket chain analyzed data on sales of a particular brand of snack cracker at 104 stores for a certain one week period. The analyst tries to predict sales based on two independent variables: (i) the total sales of all brands in the snack cracker category. (ii) whether or not there was a propmotion for a competing brand at a given store. a. Develop a linear regression model that helps predict sales b. Interpret the regression coefficients. c. Make a prediction for sales in a week where promotion is held and the sales in the entire snack cracker category is 1005.