Completion requirements
Read this chapter. Marx begins by establishing two necessary conditions for commodity production: (i) a market and (ii) a social division of labor where people make different things. For Marx, commodities both have a use-value, and an exchange-value or price, but it is the latter which is problematic. In coming to understand why one commodity is priced differently from another, Marx derives his labor theory of value.
Click on Karl Marx's Contribution to the Critique of Political Economy: Part I: The Commodity to open the resource.