Let's review the basic simple OLS regression that you have studied in the 3rd-year econometrics course. No answer key will be provided. Consider the following simple regression model. yi = a+ Bxi+ Ei i = 1, ..., n Ei~N(0, 1) 1. Derive Bols and Var(Bols). 2. State the Gauss-Markov theorem, and prove it