Some people read tea leaves to predict the future. We prefer hamburgers! The Economist began to calculate Big Mac index in 1986. They use it as a light-hearted guide to whether currencies are at their “correct” exchange rate. It is not intended as a precise predictor of exchange rates, but a tool to make economic theory more digestible. The following is the Big Mac Index in Apr. 25th 2002. 当以美元计价时，最便宜和最贵的汉堡包分别在哪里？从中可以得出有关这些国家汇率水平的什么结论？

正确答案: 最便宜的汉堡包在阿根廷，最贵的汉堡包在土耳其，这说明前者的汇率被高估，后者的汇率被低估。