Answer:
One important difference between using energy bars and using dollars as money is that ENERGY BARS have intrinsic value. U.S. dollars are an example of FIAT money.
Explanation:
Energy bars have intrinsic value and therefore present a type of commodity inside the jail. This is called commodity money because energy bars have value besides the value assigned by the prisoners. They serve as a medium of exchange but they can also be eaten.
On the other hand, fiat money or official currency has value because the government backs it. For example, the US dollar has value because the US government stands behind them: "This note is legal tender for all debts, public and private." US dollars can only be used as money, since they cannot be eaten like energy bars or traded for another use besides being money.