If e is the exchange rate, then wheat selling in England at £1.35 will sell in the United States for 1.35e + 0.5, where 0.5 is the U.S. tariff on English wheat. In order to eliminate the possibility of arbitrage, 1.35e + 0.5 must be greater than or equal to $3.25, the price of wheat in the U.S. or e > $2.0370. Thus the maximum exchange rate change that could occur is (2.4074 - 2.0370)/2.4074 = 15.38%. This solution assumes that the pound and dollar prices of wheat remain the same as before the tariff.