a. Establish the expected value in (15.94) by writing E[&] = E[(D)D'AD(D'")] and noting that D"= " = [ 17 ] M. 9, + DTX M+

E[D] = D'Xa Var[D][M.M + D'X(X!VX.) 'X'D.

b. Verify that the first term in (15.94) is zero for T. Hint: Use the procedure as in (15.86) and use (15.33) and the properties of B to write this expression as (ADBBBB100) and note that BB DA,D-0.