Question 24. Fifteen years ago, the city of Waterloo decided to implement a specialized skill-buildingeducation program - School and College Ability Training (5.C.A.T] -so that its high school graduates would be able to perform better in college and earn higher salary. Now Waterloo has asked you to evaluate the effectiveness of the S.C.A.T. program. Their data show that before the program, the average annual salary of recent high school graduates was $25,!CIEID and that now the average salary has risen to $23,500. Fortunately for your analysis, a neighboring city of Kitchener did not implement this S.C.A.T program. Fifteen years ago, recent Kitchener high school graduates earned an average of $22,500, and now that average is $23,?ED. [a] Use a difference-in-differences estimator to determine whether Waterloo's training program can sed the wages of their high school graduates to increase. [b] What underlying assumption do you have to make in order for your estimate to be valid? What might cause your underlying assumption to be invalid? (c) Su SLJLT ppose that you conduct a survey of ll students in the Waterloo- Kitchener region before and after the T program was implemented. Specify the multiple regression model you would estimate to determine whether Waterloo's training program caused an increase in sala ry