Regarding foreign exchange, analyze the following statements:
I- The exchange rate is the equivalence between two currencies, that is, the number of national coins needed to acquire a unit of foreign currency.
II- The exchange rate is only necessary for the exchange of products between countries.
III- The fixed exchange rate regime is determined by the State through its monetary authority.
IV- The flexible exchange rate regime is determined by the free market forces.
V- The tariff is the tax applied to foreign goods entering a national market.

a) I, III, IV, and V are correct.
b) I, II, and V are correct.
c) II, III, IV, and V are correct.
d) I, II, III, IV, and V are correct.