A breathing mixture used by deep sea diver contains helium, oxygen, and carbon dioxide. What is the partial pressure of oxygen at 101.4 kPa if P He = 82.5 kPa and P CO₂ = 0.4 kPa?
1) 82.9 kPa
2) 19.3 kPa
3) 18.5 kPa
4) 101.0 kPa