A lung compliance test indicates that a 3 cm H₂O change in transpulmonary pressure generates a 0.9 liter change in lung volume. What is this patient's lung compliance?
1) 0.2 liters of air/cm H₂O
2) 0.2 cm H₂O/liter of air
3) 3.33 cm H₂O/liter of air
4) 0.3 liters of air/cm H₂O
5) 2.7 liters of air/cm H₂O