Customers arrive at a ticket office window with a single clerk according to Poisson process witha mean interarrival time of 20 seconds. The office has a single clerk whose service times are i. i.d. exponential with a rateD4per minute. The service discipline is FIFO (we have an M/M/1queueing system).(a) Compute the probability that 3 or more customers will arrive within a two-minute window.(b) Customernarrived at 11:20 a. m. What is the probability that customernC2will arrive by11:22 a. m.