Can any one help me on part(c) of the following question. I did part(a),(b). Answer for (c) is 8days.
Q) A marina hires out boats on a daily basis. The mean number boats hired per day is 15. Using the normal approximation for a Poisson distribution find for a period of 100 days.
(a) How often 5 or less boats are hired
(b) How often exactly 10 boats are hired
(c) On how many days they will have to turn customers away if the marina owns 20 boats.