Processes of voluntary market exchange include willing buyers and willing sellers, and like values exchange for like. In industrial capitalism, workers sell their labour-power to capitalists for a wage and those capitalists purchase and consume worker's labour-power in the production process. The profit that capitalists receive by selling the commodities produced by labour power are greater than the amount spent on wages, machines, and materials in the production process. This is the source of capitalism accumulation. But how is this possible, if like values exchanges for like? How do capitalists make a profit? In your answer, use the concepts of use-value and exchange value.