Can you provide answers with bit explanation.

Suppose that Zi = Xi0 + oili with the (i ) known and the (ci ~ N (0, 1)). (1) The weighted least squares estimator minimizes: O E- (Zi - Oxi) /oi O ER ( zi - Oxi) 2/ 0 ? (2) Find the weighted least squares estimator 0.(3) What is E (0)? O E( 0) = 0 O E(0) = En10/0, E(0) = 21 0/0? O E(0) = (4) What is Var (0)? O Var (0) =- O Var (0) = - (ET-1 27 /0?)2 O Var (0 ) = , 2,/0? Var (0) = (5) What is the distribution of A? Student-t O Chi-squared Gamma Normal