We have seen that in production, the action of living labour: (1) preserves the value of the material and instrument whose form is changed (into that of the product); (2) reproduces its own cost of reproduction; and (3) produces a surplus value.

It follows from this that the surplus value produced in production depends for its magnitude on two factors. First, on the ratio of the capital advanced in the form of material and instrument to that advanced as labour (wages); second, on the ratio of necessary labour-time and surplus labour-time.

More (pdf, 79 KB): The Chapter on Capital: Part 15: The Transformation of Surplus Labour into Profit (II): Different Combinations of Capital (pp. 373-386)