4.2. Consider a bivariate normal population with #1 = 0, #2 = 2, 01] = 2, 022 = 1, and P12 = 5. (a) Write out the bivariate normal density.(b) Write out the squared generalized distance expression (x - /)'E (x - /) as a function of x1 and x2. (c) Determine (and sketch) the constant-density contour that contains 50% of the probability