When the exchange rate increases from $4$ francs per dollar to $6$ francs per dollar, the dollar has $\_\_\_\_\_.$

Multiple Choice

depreciated

appreciated

become overvalued

become undervalued

$$1=2$ British pounds in the United States.

$$2=1$ British pound in the United States.

$$1=$ $$0\mathrm{.}20$ British pounds in Great Britain.

$$0\mathrm{.}20=1$ British pound in Great Britain.