At this point you're familiar with cost theory. It was a tough slog, I told you it would be, but it's worth it because now that we have the understanding of these tools, of how cost curves look, and how their shape is, and their relative positions. So we have a good idea of what's happening at the production level for a firm, and now we want to think about going a little bit deeper. So what we're going to do is, we're going to step in and saying, let's think about understanding individual firm behavior. Now, we've talked about firm behavior in the past. We said, well, firms really want is to maximize profits, and I just want to remind you because I know sometimes people in the class are from the not-for-profit sector. But people in the not-for-profit sector and the people in for-profit sector still behave the same way. They're interested in maximizing the amount of residuals, sometimes in the for-profit sector those residuals turn out to be income for the owners of the firm. In the not-for-profit sector, those residuals turn out to be used for the good cause that the not-for-profit is aiming for, okay? So not-for-profits have a reason to make money because they want to devote it to this cause. And they still are interested in making sure that they run the most efficient operation, so they have the largest residuals that they can devote towards their hospital, or towards environmental concerns, or whatever their cause is. So for this video, here's what the firm knows. The firm knows, one, its own set of cost curves associated with production. Okay, those are the cost curves that we've learned to understand through some hard work in some of the previous videos, but we're also adding a little twist here. We're going to say the firm has to take an exogenously given price, that price is P sub 0. Now, exogenously given price means exactly that, it means it's a price that's given to it, and the firm has no control over it. And so what we're going to do here, is we're going to say, well, we now know a lot about costs, so we know about how much different output per decisions will change average cost, marginal cost, average variable cost, all of these things. Now, we're going to add on to that, for different possible outputs, how much money are you making? And to make life really easy, we're going to assume that the price is a constant. And we're just going to see how that manager of this firm will maximize profits, that is, make the largest residuals given this fixed price. Think of it like, for example, a corn farmer. The Board of Trade in Chicago sets the price of corn on a daily basis, the farmer may not like it. The farmer wishes to the price of corn was two dollars higher, the farmer may be groaning about it. But the farmer has no control over it, that price is set by an exogenous market, The Chicago Board of Trade. That's the type of stuff we're talking about. We're talking about taking a fixed price, which you have no control over, and optimizing given that price, and given the cost that you are aware of. Thanks.