You are an officer in the US Navy and have volunteered for submarine duty. As an environmental engineer, your job is to ensure the health and safety of all personnel on the submarine. You monitor an air purification system that automatically generates oxygen to maintain and N₂/O₂ molar ratio of 3.95 and a water vapor mole fraction of 0.0092. At what CO₂ level (in ppm (mol/mol)) must you set the alarm to ensure that the O₂ never drops below 19.5%.