6-) The Economist publishes annually the "Big Mac Index" by which they compare the prices of the McDonald's Corporation's Big Mac hamburger around the world. The index estimates the exchange rates for currencies based on the assumption that the burgers in question are the same across the world and therefore, the price should be the same. If a Big Mac costs $3.99 in the United States and 67 liras in Istanbul, a) What is the estimated exchange rate of Turkish lira per dollar as hypothesized by the Big Mac Index? b) Discuss whether the Turkish lira at the current exchange rate of 18.6 is overvalued or undervalued according to the Big Mac Index