For a dummy variable multiple regression model based on the dummy variables ????1 and ????2 and a single quantitative explanatory variable ????

(a) write down the equation of the interaction model.

(b) determine the slope of the regression line when ????1 = ????2 = 1 for the interaction model.

(c) determine the slope of the regression line when ????1 = ????2 = 0 for the interaction model.

(d) determine the slope of the regression line when ????1 = 1 and ????2 = 0 for the interaction model.