Please note that the letters inside the diagram below (such as G, H, M) refer to the shapes defined by the line segments (solid or dashed) surrounding the letter. P P4 F G P3 H L K P2 L M N R P1 MC = AC D Q3 Q2 Q1 Q MR In the diagram, the competitive market equilibrium price (without tax or other regulation) is O P1 O PA O P3 O P2