when i read the explanation part to the corollary 7.1 at page 297, i feel confused whether the strategy of fight taken by incumbent would be a nash equilibrium if the entrant enters, getting the payoff with (-1,-1). i think it should not be a nash equilibrium, because incumbent can choose acquiescing to improve his situation with a better payoff of (1,1), given the entrant`s strategy of entering fixed. although it seems like a trivial, help me.