Enterprise Industries produces Fresh, a brand of liquid laundry detergent. In order to manage its inventory more effectively and make revenue projections, the company would like to better predict demand for Fresh. To develop a prediction model, the company has gathered data concerning demand for Fresh over the last $30$ sales periods $($each sales period is defined to be a four$-$week period$).$ The demand data are presented in table below concerning y $($demand for Fresh liquid laundry detergent$),$ x$1($the price of Fresh$),$ x$2($the average industry price of competitors' similar detergents$),$ and x$3($Enterprise Industries$$ advertising expenditure for Fresh$).$ To ultimately increase the demand for Fresh, Enterprise Industries$$ marketing department is comparing the effectiveness of three different advertising campaigns. These campaigns are denoted as campaigns A$,$ B$,$ and C$.$ Campaign A consists entirely of television commercials, campaign B consists of a balanced mixture of television and radio commercials, and campaign C consists of a balanced mixture of television, radio, newspaper, and magazine ads. To conduct the study, Enterprise Industries has randomly selected one advertising campaign to be used in each of the $30$ sales periods in table below. Although logic would indicate that each of campaigns A$,$ B$,$ and C should be used in $10$ of the $30$ sales periods, Enterprise Industries has made previous commitments to the advertising media involved in the study. As a result, campaigns A$,$ B$,$ and C were randomly assigned to$,$ respectively, $9,11,$ and $10$ sales periods. Furthermore, advertising was done in only the first three weeks of each sales period, so that the carryover effect of the campaign used in a sales period to the next sales period would be minimized. Table lists the campaigns used in the sales periods.