3.31 The interarrival time T between "hits" on a certain web page is an exponential random variable with parameter 1 = 0.5 hits/minute. The average interarrival time is given by 1/1. (a) What is the probability that the interarrival time between hits is greater than twice the average interarrival time? (b) What is the probability that the interarrival time between hits is less than half the average interarrival time? (c) What are the answers to parts (b) and (c) if a changes to 10 hits/min?