To determine a subject’s total lung volume, you have them breath into a 2 L cylinder of gas with initial concentration of 15% He by volume. The subject breaths for about a minute. After a large inhale the subject holds her breath and you measure the He concentration to be 4%.

(a) What is the subjects total lung volume?

(b) What assumptions/experimental conditions must you make for this experiment to be valid?

(c) You now have the subject exhale deeply and measure the He concentration to be 10%. What lung volume does this measure (state your assumptions if needed) and how large is this volume?