A customer service center has customers call with questions about the use of a product. The mean arrival rate of customer calls is 20 per hour and follows a Poisson distribution. The mean service rate (how long it takes the call center employee to answer the customer's question) is 30 customers per hour (most customer questions can be answered rather quickly) and follows an Exponential distribution.
What is the mean (average) time in hours that a customer spends in the system (waiting on hold, then having their question answered)?
What is the mean utilization percentage of the call center employee answering the phones (the server in this system)?