Assume customers arrive at a rate of two every minute. Suppose the number of customers in any time interval has a poisson distribution.

a) if a clerk takes 3 minutes to serve the first customer arriving at the counter, what is the probability that at least one more customer will be waiting when the service provided to the first customer is completed?
b) let T3 be the time in minutes from opening until the third customer arrives. What is the distribution of T3? Find P(T3>2).