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. But you might say, well, why do I even care about the rate at which my costs are increasing, the rate at which my costs are increasing on the margin, which is why this is called marginal cost. Well, the reason why you care about it is you might be trying to figure out when do I stop producing? Let's say this is orange juice. If I know that next gallon is going to cost me $5 to produce, and I can sell it for $6, then I'm gonna do it. But if that next gallon, if I'm up here, I've already produced a lot, and I'm taking all the oranges off the market, and now I have to transport oranges from the other side of the planet or whatever it might be, and now that incremental gallon of oranges or a gallon of orange juice costs me $10 to produce, and I'm not going to be able to sell it for more than $6, it doesn't make sense for me to produce it anymore. So in a calculus context, or I guess you say in an economics context, if you can model your cost as a function of quantity, the derivative of that is the marginal cost.