Engine 2014: Steam Plants

1. A piston "F" moves upward to open the exhaust valve and close the makeup steam valve.
2. B piston "F" moves upward to close the exhaust valve and open the makeup steam valve
3. C piston "F" moves downward to close the exhaust valve and open the steam makeup valve
4. D piston 'F" moves downward to open the exhaust valve and close the steam makeup valve

Tip: press A-D to answer