The following are the design matrix x, response vector Y, and (xx)-1 for a multiple linear regression model. 1 0 1 1 0 2 1.33 -0.33 -0.50 0 3 Y = (x'x)" = -0.33 0.67 0.00 1 1 1 -0.50 0.00 0.25 1 1 2 1 3 (a) Calculate the least squares estimates of the model y = Po + 1x1 + 2x12 + for i = 1,..., n. (b) Calculate an unbiased estimate for the variance of the random errors. (c) Calculate a 95% confidence interval for B. (d) Briefly explain an implication of the O's in the (xx) matrix. 1,400 x 662