Before world war i, $20.67 was needed to buy one ounce of gold. if, at the same time one ounce of gold could be purchased in france for ff410.00, what was the exchange rate between french francs and u

Before world war i, $20.67 was needed to buy one ounce of gold. if, at the same time one ounce of gold could be purchased in france for ff410.00, what was the exchange rate between french francs and u.s. dollars (in 2 decimals)?