A random number of jobs are to be processed sequentially on a single processor. The processing times of the jobs and the total number of jobs are mutually independent random variables. The number of jobs has mean 5 and variance 2, and each job's processing time has mean 2 and variance 1. What are the mean and variance of the total sum of processing times? A random number of jobs are to be processed sequentially on a single processor. The processing times of the jobs and the total number of jobs are mutually independent random variables. The number of jobs has mean 5 and variance 2, and each job's processing time has mean 2 and variance 1. What are the mean and variance of the total sum of processing times? 8, 15 6, 12 10, 13 12, 16 10, 12