John, an assistant in the district sales oice of a national oosmetils rm, obtained the following data in 14 districts: District D M P 3 District D A! P S 1 4.2 4.0 3.0 82.5 S 4.3 4.0 5.0 107.7 2 6.5 6.5 5.0 147.0 9 2.6 2.5 5.0 75.5 3 3.0 3.5 4.0 97.3 10 3.1 3.0 4.0 89.0 4 2.1 2.0 3.0 56.2 11 5.2 6.0 4.5 125.1 5 2.9 3.0 4.0 73.4 12 5.5 5.5 5.0 104.5 6 7.2 7.0 3.0 121.8 13 2.2 2.0 4.0 71.5 7 4.8 5.0 4.5 35.6 14 3.0 2.8 3.0 67.4 where D (in 51000 per month) is the expenditure on displays in beauty salons and department stores, M (in 31\"!) per month) is the expenditure on local media, P (in percentage} is the prorated share of national media advertising, and S [in $1000 per month] is the amount of sales. John's aim is to be able to obtain a linear model to forecast the amount of sales in a district. a} Without using any soitware, obtain the estimated standardized model