please solve

Consider an innitely repeated oligopoly game in which the stage game is a Bertrand game (each player's action is a price, the lowest price gets all the demand, ties are split equally). There are n > 1 rms, the industry demand function is Q(p) = 100 p, and each rm has constant marginal production cost c = 20. Each rm has the same discount factor, 5 6 (0,1). Find the values of 6 for which a Nash reversion equilibrium exists in which, on the equi- librium path, each rm charges the monopoly price