If the official exchange rate of the British pound sterling were changed from $2.80 to $2.40 under an adjustable pegged exchange rate system, the pound sterling would be
a. revalued and appreciated against the U.S. dollar
b. revalued but not appreciated against the U.S. dollar
c. devalued and depreciated against the U.S. dollar
d. devalued but not depreciated against the U.S. dollar
Please provide specific answer and explain.