Well, here we are in sunny San Francisco, taking a cable car down to North Beach. For those who do not know the Bay area, that's Alcatraz in the background. Let us imagine that you are the driver. Let us further imagine that the cable suddenly snaps, the friction brake is too weak to hold you, and you hurtle down the hill out of control.
Indeed, let us further imagine that the only thing under your control is switching: whether to switch left onto the reversing loop at the bottom, or whether to switch right round the reversing loop. On the left-hand branch there are five people, who will be unable to get out of the way in time. On the right hand branch there is one such person.
