Use the Information Below to Answer the Following Question(s)

Multiple Choice

Use the information below to answer the following question(s) .
A steady stream of eager fresh-faced students waits in line to register for classes before the start of fall semester classes.Students arrive at the rate of 10 per hour and it takes the single clerk on duty an average of 3 minutes to check their student status,and register them for classes.The service time is exponentially distributed.
-What is the service time in number of students serviced per hour?

A) 20
B) 45
C) 60
D) 90