Bob has a monopoly in the market of wireless widgets, and Alice is considering competing with Bob. If Alice does not enter the market, her payoff is zero, and Bob makes a three-billion-pound profit. If Alice enters the market, Bob can either fight her off by reducing prices so that he makes zero profit and Alice loses a billion pounds, or Bob can choose not to fight her, and they both end up making a profit of a billion pounds. Find the Nash equilibrium for this sequential game. A. (enter, fight) B. (do not enter, fight) C. (do not enter, do not fight)