How to solve

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 rat is 30 customer per hour and follows an exponential distribution.

What is the mean 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?

What is the mean number of customers that are on hold, waiting for their call to be answered?

If the company decides to hire a second person to answer calls, the waiting time should be faster. On average, how long will a customer now wait on hold for their question to be answered?