Question

Karl Marx and Henry George argued that all labor is exploited. Natural resources and labor produce all products and capital is just a combination of natural resources and labor from a previous period. Any value in addition to natural resources is thus created by labor. Profits are just value created by labor but not paid to labor. This is a powerful critique of capitalism. J.B. Clark developed cost curves and a theory of the firm to disprove this claim by Marx and George. What did J.B. Clark argue instead?