In a country, one can get from some point A to any other point either by walking, or by calling a cab, waiting for it, and then being driven. Every citizen always chooses the method of transportation that requires the least time. It turns out that the distances and the traveling times are as follows: 1 km takes 10 min, 2 km takes 15 min, 3 km takes 17.5 min. We assume that the speeds of the pedestrian and the cab, and the time spent waiting for cabs, are all constants. How long does it take to reach a point which is 6 km from A? algebracombinatoricsdistancetime