Suppose that time between two telephone calls at an office, in minutes, is uniformly distributed on the

Question:

Suppose that time between two telephone calls at an office, in minutes, is uniformly distributed on the interval [0, 20]. If there were 15 calls,
(i) What is the probability that the longest time interval between calls is less than 15 minutes?
(ii) What is the probability that the shortest time interval between calls is greater than 5 minutes?