Calculating the expectation and variance of an estimator

3. (15 points) Consider the following model: yi =Bx; + &; for i = 1, 2, . .., n where E(&;) = 0 and Var(&;) = o' for all i and E(&g)= 0 for i not equal to j Calculate the expected value and variance of the following estimator of B: Vi for x+0 WE