Equilibrium Under Perfect Competition By firm’s equilibrium we mean the determination of such an output where profits are maximized; or if it has to face the losses, they must be minimized. Accordingly, a firm will be in equilibrium where the difference between TR (Total Revenue) and TC (Total Cost) is maximum. Mathematically, a firm will be in equilibrium where slope of TR (MR) is equal to slope of TC (MC). So, where MR = MC. This is called necessary condition for firm’s equilibrium. We have also a sufficient condition which states that “At equilibrium MC must cut MR from below.” In other words, slope pf MC must be greater than slope of MR. Hence, slope of MC > slope of MR. In the diagram, firm is not in equilibrium at A, because the necessary condition (MR=MC) is P cutting MR from above. This shows that MC of a firm is still falling – need is to expand output. At B and D none of the conditions of equilibrium is met. Accordingly, the firm will be in equilibrium at C. COMPOSED BY: Khashif Sarfraz