 Once we've gone through demand and how we start with its definition and then a numerical example of an individual's demand combining with other people to get the market demand, then plotting out the demand curve for the market and then talking about generic demand curves and what the law of demand means in that context, once we go through all that, it's really straightforward to do the opposite side for what's called the supply side. So by definition, the supply is simply a relationship between various hypothetical prices for a good or service on the one hand and then there's those mapped to the quantity that either the individual seller or a group of sellers want to sell at those different prices. So demand refers to the buyers, supply refers to the sellers. So again, let's just take a step back here. What are we doing? What's the big picture? With the supply and demand framework, again, we're not giving a theory of where prices come from. All we're doing is organizing our thoughts. We're saying there are, in principle, millions of different factors that go into how many units of a good the buyers want to buy and how many units of that same good the sellers want to sell. And so with supply and demand, what we're doing is we're saying, let's hold everything else fixed except the price because we think that the price may be an important factor and so that's the one we're going to focus on. So we're going to hold everything constant and then say as we alter the price, what happens to the quantity demanded and then that relationship is what we've walked through as demand and we can express it as a schedule like in the form of a table or we can plot it out in an XY plane graphically and that's what we would call a demand curve and it can be for an individual or it can be for the whole market. With supply, we can do the same thing and in the textbook, I go through the individual market supplies of gasoline for a Tuesday afternoon and so now instead of the individual consumers, we're talking about quick mark and filler up is to representative gas stations and I also have Farmer Jim in here as well and the idea is that Farmer Jim had a lot of gasoline on hand that he was going to use for his equipment but if the price of gasoline for some reason should get really high to six dollars a gallon or higher, then he's going to offer 20 gallons on the market just because he's realizing that's an abnormally high price and he would rather sell at that price and then buy later when the price comes back down for his needs on the farm. So as with demand, there's nothing scary or mysterious about supply. You're just saying list a bunch of hypothetical prices for each person on the supply side for each potential supplier, how many units would he or she sell at that price and then you sum them up horizontally to get the market quantity supplied at each hypothetical price. Now in case this is tripping you up, notice in principle you could have everybody in the whole community being on the supply and the demand side in the way what would happen though is for people who aren't ever going to sell for every possible price, you would just list zeros. So that's not going to change the answer and so if that makes you feel more comfortable, you could do it like that and have everybody as always both a supplier and a seller or sorry, a supplier and a consumer or a supplier and a demander, but for simplicity when we do these things usually we just include the people who might actually have a positive number in there. Okay, so then in the book we just walk through plotting the supply schedule to give you the supply curve and then here we see what's called the law of supply and as you may be able to guess at this point the law of supply just says as the price increases the quantity supplied either stays the same or increases. So in graphical form the law of supply says that supply curves are upward sloping and then of course the generic supply curves that we draw would just be a nice curve that's upward sloping or just a straight line that has a positive slope.