You are given the following population regression function: = 1 + . , a. Derive an expression for 1 using ordinary least squares. b. Derive an expression for the variance of 1. c. Derive the residual sum of squares (RSS)? d. Does the expression for 1 make intuitive sense? e. Now consider the two-variable model = 1 + 2 + . Is it worth adding to the model? If not, why bother with regression analysis?