# As all the world knows, the North-going Zax always goes northand the South-going Zax always goes sou

As all the world knows, the North-going Zax always goes northand the South-going Zax always goes south. Assume neither looksanywhere but straight ahead. When roads are built around them, theyremain unflinching.   Suppose two gas stations are built,one directly behind the north-going Zax and the other directlybehind the south-going Zax such that each Zax only can see thestation behind the other. Over the course of many days, thenorth-going Zax notices that the price of gas rising at the stationit can see. It also has observed you deliberately choosing to buygas at this station. You buy nothing else, just gas. During a pausein their quarreling, ‘South’ confirms that it has never seen youbuy gas at the station it can see (but it also has noticed theprice of gas rising). Given this scenario, why would you choose tobuy gas at a station which is raising its price of gas? There may be several possible answersbut there is one clear, best answer. . . .