Consider the model Y B,X + U, where E(UX)-0. In particular, we assume that the intercept is equal to 0 (which may or may not be true in the population). The data is a random sample of size n, {Yi, Xi}: i-1,2,...,n. a. (10 points) Consider the estimator E, X,Y 1 n Is B1 an unbiased estimator of B,? Is B, a consistent estimator of B1? b. (5 points) Assume that Xi#0 (Xi is the first observation of the regressor in the sample) and consider the estimator Is B, an unbiased estimator of B,?