Problem 7: Consider the linear model E01) = ,9 X; where Var(l'})= 02. (a) Write out explicitly in terms of the Y \"s and X's; what the least squares estimator of B is {call it If?) and give an explicit expression for Var( E). (b) An alternate estimator arises by considering Z t = Yi/Xi. (i) Show that Z = 2L1 Zi is an unbiased estimator for [3. (ii) Find the variance on and show directly that this variance is greater than or equal to the variance obe