What are differences between cournot oligopoly outcome and

Question

(a) What are differences between Cournot oligopoly outcome and monopoly outcome in terms of the equilibrium price and quantity?

(b) Explain why it is difficult to maintain a Cartel agreement (other than it is illegal).

(c) Explain the key differences between Cournot oligopoly, Bertrand oligopoly, and Stackelberg oligopoly.