Customers Arrive Every Three Minutes Governed by a Poisson Distribution

Multiple Choice

Customers arrive every three minutes governed by a Poisson distribution.A single server is capable of handling twenty-five customers per hour and this service time is exponentially distributed.About how many minutes per hour is the server not helping customers?

A) less than or equal to 7
B) greater than 7 but less than or equal to 10
C) greater than 10 but less than or equal to 13
D) greater than 13