Currently, there is an incumbent monopoly in a market. A potential entrant may enter.

Currently, there is an incumbent monopoly in a market. A potential entrant may enter. The incumbent can spend X dollars lobbying to require all new firms that enter the market to use a pollution-abatement device that costs Y dollars to install. If lobbying occurs, the pollution-abatement device will be required. Draw the game tree describing this situation. Under what conditions will the monopoly lobby?