Consider the problem described at the end of Section 2-6, running regression and only estimating an intercept: Given sample {y_i = 1,2, n}, let B0 be the solution to min 4g - B0. Show that B0 is the sample average that minimizes the sum of squared residuals. (Hint: You may use one-variable calculus or you can show the result directly by adding and subtracting inside the squared residual and then doing a little algebra.) Define residuals as yi - y. Argue that these residuals always sum to zero.