Suppose that you are dealing with a American call on currency, and that the foreign currency has risk-free rate 0. Explain why, in this case, the American call always has the same price value as a European call with the same expiration time and strike price. Assuming that put-call duality holds for American puts and calls, this should then mean that the option, viewed from the foreign perspective, is an American put for which it is never advantageous to exercise before expiration. Reconcile this with the example from class used to show that a put on a value-less stock should always be exercised as soon as possible.