The term marketing mix refers to the different components that can be controlled in a marketing strategy to increase sales or profit. The name comes from a cooking-mix analogy used by Neil Borden in his 1953 presidential address to the American Marketing Association. In 1960, E. Jerome McCarthy proposed the "four Ps" of marketing—product, price, place (or distribution), and promotion—as the most basic components of the marketing mix. Variables related to the four Ps are called marketing mix variables.

A market researcher for a major manufacturer of computer printers is constructing a multiple regression model to predict monthly sales of printers using various marketing mix variables. The model uses historical data for various printer models and will be used to forecast sales for a newly introduced printer.

The dependent variable for the model is:
y= sales in a given month (in thousands of dollars)

The independent variables for the model are chosen from the following marketing mix variables:

x1= product feature index for the printer (a score based on its quantity and quality of features)
x2= average sale price (in dollars)
x3= number of retail stores selling the printer
x4= advertising spending for the given month (in thousands of dollars)
x5= amount of coupon rebate (in dollars)

The market researcher decides to predict sales using only the average sale price, the advertising spending for the given month, and the amount of the coupon rebate. Write down the multiple regression.