3. We are interested in the estimation of 51 from the following multiple regression model: Y: = 31X1i+ zXai + 8:, 8.- ~ *i.*i.d.N[D,o'2} a} The 1 coefcient from the above multiple regression equation can be estimated by running three simple regression equations, each of which consists of only one regressor. Explain each of the three steps. 1:} Provide an intuitive explanation on why the estimator of 1:31 obtained from the third step may be unbiased. c] Provide an 0L3 estimator of {31 and its variance from the third step. Then, discuss what happens if there exists near multicollineerity. .n