suppose that ex is the exchange rate between the U. dollar and the Chinese yuan in that ex indicates the number of yuan that can be purchased with...

suppose that ex is the exchange rate between the U.S. dollar and the Chinese yuan in that ex indicates the number of yuan that can be purchased with one dollar. The demand for dollars, denoted, D$, is given by the equation D$ = 2,800 - 200ex. The supply of the dollars, denoted, S$, is given by the equation S$ = 400 + 100ex.