Let Bo and B, denote the OLS estimator of the intercept and slope of the simple linear regression model yi = Bo + Bix; + ci, i = 1, . ..,n, where E 's are independent errors with E(6;) = 0 and Var(ci) = 02. a. Prove that Cov(y, B1) = 0. b. Let ei = yi - (Bo + B1 2) be the residual. Prove Ciej = 0