The correct answer is: E. Chamberlin.
Edward Chamberlin was an American economist who is best known for his work on monopolistic competition. He coined the term “selling cost” in his 1933 book “The Theory of Monopolistic Competition.” Selling costs are costs that a firm incurs in order to promote its product or service, such as advertising, marketing, and sales promotion.
A. P. Samuelson was an American economist who is best known for his work on general equilibrium theory. He did not coin the term “selling cost.”
A. Marshall was a British economist who is best known for his work on microeconomics. He did not coin the term “selling cost.”
Joan Robinson was a British economist who is best known for her work on imperfect competition. She did not coin the term “selling cost.”