Customers Arrive at a Ticket Counter at the Rate of 50

Customers arrive at a ticket counter at the rate of 50 customers per hour, according to a Poisson distribution. There are three ticket agents. Customers select the first available agent from one line. Each agent can process 20 customers per hour with exponential service times.
-Use the information in Scenario C.4.What is the average time spent in the system?

A) Fewer than or equal to 6.5 minutes
B) Greater than 6.5 minutes but fewer than or equal to 7.5 minutes
C) Greater than 7.5 minutes but fewer than or equal to 8.5 minutes
D) Greater than 8.5 minutes