You are waiting for a bus which takes a round trip of 10 minutes to complete (starting again when it finishes one tour). What is your expected waiting time if you arrive at a random time (uniformly from 0 to 10 minutes)? Next, consider that there is an ice cream shop somewhere on the bus route; every time the bus passes it, the driver flips a fair coin and, if heads, spends 10 minutes eating ice cream before continuing the tour. What is your expected waiting time now? How does the answer change if the coin is biased?