1, In a particular departmental store customers arrive at a check up counter

according to poisson distribution at an average of 5 per hour

During a particular 1 hour period,

a,what is the probability that at least 3 customers will arrive

b,What is the probability that in a given 2 hours period exactly 2 customers will arrive

c,In a 30 minute period determine the probability that at most 2 customers will arrive