Service Management 7th Edition by James Fitzsimmons, Mona Fitzsimmons

Exercise 8

You show up early in the morning to buy tickets for a concert but you find a long line and are told that the average time between arrivals has been about 15 minutes.
a. What is the chance you will loose my place at the end of the line, if after just arriving, you leave for 5 minutes to use the restroom?
b. What is the probability that zero, one, or two arrivals will come during your five minute rest break?