A local commuter bus service advertises that buses run every 15 minutes along a certain route. Assume that the bus service follows an exponential distribution. What is the probability of a bus picking up the passengers at a given bus stop in no more than 15 minutes? What is the probability of a bus picking up the passengers at a given bus stop in more than 15 minutes? What is the probability of a bus picking up the passengers at a given bus stop in between 15 and 25 minutes?