That is, if a person can purchase a good for price S and conclude a contract to sell it one month later at a price of F, the price difference should be no greater than the cost of using money less any expenses (or earnings) from holding the asset; if the difference is greater, the person has an opportunity to buy and sell the "spots" and "futures" for a risk-free profit, i.e.
If someone buys an item at price S and agrees to sell it one month later at price F, the difference in cost should not exceed the expenses (or earnings) of using money less any fees; if this difference is larger, the individual can buy and resell "spots" and "futures" for a risk-free profit.