2. (8 points) Let be the slope estimate from a simple regression of y on x, and assume that there is variation in the sample values of both y and x. 2.1. Derive an expression for R in terms of the slope estimate, ; the sample variance of x, Var(x); and the sample variance of y, Var(y). Hint: Express R as a ratio of two variances, then use the formula for the estimated regression line. If = 0, must it be that R = 0? 2.2. If R = 0, must it be that = 0?