Class 12 Economics Chapter 4 The Theory of the Firm Class 12 Economics Chapter 4 PDF NCERT Solutions for Class 12 Economics Chapter 4 The Theory of the Firm. PDF Download Free. Chapter 1 Introduction Chapter 2 Theory of Consumer Behaviour Chapter 3 Production and Costs Chapter 4 The Theory of The Firm Chapter 5 Market Equilibrium Chapter 6 Non-Competitive Markets