Commodities also trade in the futures market. So a commodity futures contract is a contract where you agree to buy or sell a prearranged amount of a certain commodity at a specific price on a specified future date. And that's also when you will pay. Most contracts are settled in cash, so that means if you've benefited in your contract, you'll receive cash. If you've lost on your contract, you'll pay cash. But some contracts dictate physical delivery. So that means if you bought, for instance, oil in the futures market, when it's time for expiry, you might get delivery of a number of thousands of barrels of oil in a specified location. So what are the prices like in the future's market? Well, we start by looking at the spot price. The spot prices is the starting point in figuring out what the future prices are going to be. But then on top of that, we adjust that spot price for things like storage costs. So higher storage costs will lead to higher future prices. And we also look at the risk-free rate or the interest rate, and of course how long in the future delivery is. So a very simplistic way of calculating the futures price here is looking at the spot price. Add to that storage costs, and multiply that by E to the power of the risk-free rate, times the time to delivery. And E here is ER's number. Don't worry if you don't understand this ER's number thing. It's simply an expression reflecting the fact that we're compounding the interest rate on a daily basis.