Each of the following had a theory of profit except

A) Karl Marx.
B) Joseph Schumpeter.
C) Frank Knight.
D) Pierre-Joseph Proudhon.

Theory of Profit

A concept that explains how profit emerges from the difference between a firm's revenues and its costs and how it acts as an incentive for business operations.

Joseph Schumpeter

An economist known for his theories on business cycles, innovation, and economic development, including the concept of "creative destruction."

Karl Marx

A 19th-century philosopher, economist, and political theorist known for his critique of capitalism and his influential ideas that led to the development of Marxism.