Todays exchange rate between the yuan and the U.S. dollar is 6.78 yuan per dollar and the

Question:

Today’s between the yuan and the U.S. dollar is 6.78 yuan per dollar and the central bank of China is buying U.S. dollars in the foreign exchange market. If the central bank of China did not purchase U.S. dollars would there be excess demand or excess supply of U.S. dollars in the foreign exchange market? Would the remain at 6.78 yuan per U.S. dollar? If not, which currency would appreciate?
Exchange Rate
The value of one currency for the purpose of conversion to another. Exchange Rate means on any day, for purposes of determining the Dollar Equivalent of any currency other than Dollars, the rate at which such currency may be exchanged into Dollars...