2. [20 points] Consider Bertrand oligopoly studied in class. That is, n > 2 idential firms with the same market demand function and the same linear cost function. Main the same assumptions as we did in class. Prove that the only possible Nash equilibrium for this model is such that: (i) the minimum of the prices charged by all firms is equal to the marginal cost; (ii) there are more than one firm charging this price