The Exponential Distribution · Exercise 41

A web site experiences traffic during normal working hours at a rate of 12 visits per hour. Assume that the duration between visits has the exponential distribution.

(a) Find the probability that the duration between two successive visits to the web site is more than ten minutes.
(b) The top 25% of durations between visits are at least how long?
(c) Suppose that 20 minutes have passed since the last visit to the web site. What is the probability that the next visit will occur within the next 5 minutes?
(d) Find the probability that less than 7 visits occur within a one-hour period.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Introductory Statistics 2e · §5.3 The Exponential Distribution · Exercise 41