U. He does odd jobs to supplement his income. Job requests come every 5 days on the average, but the time between requests is exponential. The time for completing a job is also exponential with mean 4 days a) What is the probability that John will be out of jobs? b) If John gets about $50 a job, what is the average monthly income? c) If at the end of the semester, John decides to subcontract on the outstanding jobs at $40 each. How much, on the average, should he expect to pay?