9- In the multiple linear regression model Y=Bo + BIX1 + 82X2 + u, use matrix formulation to show what happens to the least squared solution of the parameters, B = (X'X) 'X'Y and R? =1-SSR/SST when a. Y is multiplied by a constant, c. b. All Xs are multiplied by c.~ c. Y and Xs are all multiplied by c