32. There are three jobs and a single worker who works first on job 1, then on job 2, and finally on job 3. The amounts of time that he spends on each job are independent exponential random variables with mean 1. Let Ci be the time at which job i is completed, i = 1, 2, 3, and let X = 3 i=1 Ci be the sum of these completion times. Find

(a) E[X],

(b) Var(X).