probability problem

(10 points) Assume that the interarrival times At1, At2, At3, ..., Atn for n customers into a post office are exponential with parameter 2, so that Att ~ Exp(a) for k = 1, 2, 3, ..., n. Compute the theoretical probability that no two customers arrive within a time 0 > 0 of each other. Your final answer should involve only n, A and 0. Note that this is one way to address the crowed arrivals of customers