An LPG (Liquified Petroleum Gas) cylinder weighs 15.0 kg when empty. When full, it weighs 30.0 kg and shows a pressure of 3.0 atm. In the course of usage at 27°C, the mass of the full cylinder is reduced to 24.2 kg. The volume of the used gas in cubic metre at the normal usage condition (1 atm and 27°C) is (assume LPG to be normal butane and it behaves ideally):