Stock market analysts are continually looking for reliable predictors of stock prices. Consider the problem of modeling the price per share of electric utility stocks (Y). Two variables thought to influence such a stock price are return on average equity (X₁) and annual dividend rate (X₂). The stock price, returns on equity, and dividend rates on a randomly selected day for 16 electric utility stocks are provided in the file P13_19.XLS.
a. Estimate a multiple regression model using the given data. Include linear terms as well as an interaction term involving the return on average equity (X₁) and annual dividend rate (X₂). 

b. Which of the three explanatory variables ((X₁, X₂, and X₁ X₂) should be included in a final version of this regression model? Explain. Does your conclusion make sense in light of your knowledge of corporate finance?