Problem 5. (12 marks in total) two clerks are on call at FastService LTD. Customers arrive at a mean rate of 1 per minute, and, on average, it takes 2 minutes to serve a customer. It has been observed that, on average, customers wait 1.5 minutes before being served. (a) (3 marks) on average, how much time a customer waits at FastService LTD? (b) (3 marks) what is the average length of the queue at FastService LTD? (c) (3 marks) what is the average number of customers at FastService LTD? (d) (3 marks) what fraction of the time is the system empty?