There are three types of money: commodity money, commodity-backed money, and fiat money. Which type of money is used in each of the following situations?

a. Bottles of rum were used to pay for goods in colonial Australia.

b. Salt was used in many European countries as a medium of exchange.

c. For a brief time, Germany used paper money (the "Rye Mark") that could be redeemed for a certain amount of rye, a type of grain.

d. The city of Kamloops, British Columbia, prints its own currency, the Kamloops dollar, which can be used to purchase local goods and services.