Engine 2014: Steam Plants

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

Tip: press A-D to answer