An ambulance service receives an average of 15 calls per day during the time period 6 p.m.

Question:

An ambulance service receives an average of 15 calls per day during the time period 6 p.m. to 6 a.m. for assistance.
For any given day what is the probability that fewer than 10 calls will be received during the 12-hour period? What is the probability that more than 17 calls during the 12-hour period will be received?