The conclusion doesn’t assert any causal relationship. It simply asserts that the first economies were based on barter, and money came later. This doesn’t say barter caused money to come about, or that anything caused barter.

The premises do not contradict each other. It can be true that when money disappeared, places turned to a barter economy. Then, when money was available again, the economy turned back into one based on money.

The conclusion doesn’t assert that anything “should” be done. The author does not issue a command or recommendation or display any kind of value judgment. The conclusion is simply a descriptive one concerning whether the first economies were barter-based or money-based.

The author does not conclude or assume any causal relationship. He simply asserts that the first economies were based on barter, and money came later. This doesn’t imply barter caused money to come about, or that anything caused barter.

(E) accurately describes the circular reasoning of the argument. A premise, in describing how an economy “reverts to the original barter system” presupposes what the argument atttempts to show in the conclusion — that the very first economies were based on barter.