In an Ordinary 8-Hour Day, Roto-Drains Receives Calls for Emergency

Multiple Choice

In an ordinary 8-hour day, Roto-Drains receives calls for emergency service at an average rate of 1 per hour (otherwise, the calls appear to be random and independent) .The owner currently has a crew of technicians capable of handling up to (and including) nine emergencies per day.She is considering expanding the crew.If she wants to ensure that there is less than a 5% chance that the crew won't be able to handle the emergency load, she will need a crew that can handle up to (and including) how many emergencies per day.

A) 13
B) 12
C) 15
D) 11
E) 10