Question 85
The country of Cathay has four cities with airports and two Airlines Cathay Red and Cathay Blue. Each of the six routes is assigned to only one of the airlines. No airline is assigned all the routes. An assignment of routes is called good if there are two cities for which the airline that operates the route between the two is different from the airline that operates the route between the other two cities. Show that there is an assignment of routes which is not good.