Prove the following:
(a) A random variable created by Algorithm 3.2.2 is a two-stage hyperexponential random variable having the properties claimed.
(b) A random variable created by Algorithm 3.2.3 is a two-stage hyperexponential random variable having the properties claimed.
(c) A random variable created by Algorithm 3.2.4 is a two-stage hyperexponential random variable having the properties claimed.