Recreational scuba diving using air is limited to depths of 40 m. Technical divers use different gas mixes at different depths, allowing them to go much deeper. Assuming a lung volume of 6 liters, estimate the mass of air in the lungs of:
(a) A person at atmospheric conditions.
(b) A recreational diver breathing air at a depth of 40 m below the ocean surface.
(c) A near-world-record technical diver at a depth of 300 m below the ocean surface, breathing 10 mol% oxygen, 20 mol% nitrogen, 70 mol% helium.