Solution:A monopoly firm does not always earn super normal profits. rather than
(i) In the long run, if the super normal profits continue it will attract other producer to enter market and the monopoly will lose these profit and may have to shutdown its production if it incurs loses
(ii) Sweezy's kinked demand curve model is the best known model explaining relatively more satisfactory behaviour of oligopoly firm for price rigidity.
(iii) A perfectly competitive firm is price taker not price maker.
(iv) firm under monopolistic completion earn only normal profits in the long run.