4. Suppose that we observe statistically independent observations Y for i = 1,2 and j = 1,2 with the same variance o', where E(Y,,) is modeled as follows: E(Yn1) = #, E(Y12) = #+7, E(Ya) = uta, E(Y2) = ptaty. Suppose that Yn is missing (not available), in other words, the dataset we have Y12, Y21, Y22. Then, what happens for LSEs of p, a and y