Answer:
The ansewr is a barter based economy.
In a barter based economy, goods are exchanged for other goods, because no good that takes the functions of money exists (unit of account, store of value, and medium of exchange).
Barter economies can work on a limited scope, but to a larger extent, they can become inefficient, because this type of economy requires a double coincidence of wants: both parties of the transaction must desire the other party's goods.
