6.
the value of one good in a trade as compared to another good.
a) exchange rate
b) double coincidence of
want
c) surplus
d) the barter system

The value of one good in a trade as compared to another good is termed as exchange rate.

Option A

Explanation:

The exchange rate has become more popular now for its use with respect to a currency like on conversion value of one currency to another. The earlier exchange rate was understood with respect to the barter system which was used before the invention of money and followed up to centuries, it involved goods and services exchange among people.

Double coincidence of wants became the foundation of the bartering economy without the involvement of monetary as the medium. The surplus is leftover goods and services after completing requirements also called excess production.

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