If our cost function were a line, we would have a constant slope. The tangent line would essentially be the cost function. But we see it changes right over here. The incremental atom to produce here costs less than the incremental atom right over here. The slope has gone up. And it might make sense. Maybe I'm using some raw material out there in the world, and as I use more and more of it, it becomes more and more scarce, and so the market price of it goes up and up and up.