The author of ‘Economic Theory and Operations Analysis’ is

Robbins
Keynes
Bamol
Marshall

The correct answer is: C. Bamol

William J. Baumol is an American economist who is known for his work on industrial organization, public economics, and the economics of the arts. He is the author of numerous books, including “Economic Theory and Operations Analysis” (1959), “Business Behavior, Value and Growth” (1959), “The Theory of Price Discrimination” (1964), “Economics of the Public Sector” (1965), “Wealth and Welfare” (1968), “The Cost Disease of the Service Sector” (1967), “The Free Market and the Arts” (1978), “Superfairness: Choosing Among Three Values in Social Choice” (1985), “The Productivity Puzzle” (1991), “To Promote Growth: Innovation and the Wealth of Nations” (2002), and “The Free-Market Innovation Machine: Analyzing the Growth Miracle of Capitalism” (2004).

Robbins, Keynes, and Marshall are all well-known economists, but they did not write a book called “Economic Theory and Operations Analysis.”