A study of climbers who reached the summit of Mount Everest without supplemental oxygen showed that the partial pressures of O₂ and CO₂ in their lungs were 35 mm Hg and 7.5 mm Hg, respectively. The barometric pressure at the summit was 253 mm Hg. Assume the lung gases are saturated with moisture at a body temperature of 37°C [which means the partial pressure of water vapor in the lungs is P (H₂O) = 47.1 mm Hg]. If you assume the lung gases consist of only O₂, N₂, CO2, and H₂O, what is the partial pressure of N₂?