3.31. The random variable r takes on the values l 2. or 3 with probabilities (1 3k)/3, (l 2k)/3, and (0.5 5k)/3, respectively. (a) Find the appropriate value of k. (b) Find the mean and variance of u. (c) Find the cumulative distribution function. a 3.32. The probability distribution of the discrete random variable r is p(x) kr 0 r 1. Find the appropri ate value for k if 0. 1.... 3.33. A manufacturer of electronic calculators offers a one-year warranty. If the calculator fails for any reason during this period, it is replaced. The time to failure is well modeled by the following probability distribution: f(x) 0.125e -0.125 c 0 (a) What percentage of the calculators will fail. within the warranty period? (b) The manufacturing cost of a calculator is $50. and the profit per sale is $25. What is the effect of warranty replacement on profit?