At sea level, P = 1 atm, therefore gas solubility is x = 1atm * molar fraction of gas. For O2 = 0.2 atm/773 atmkgH₂O/mol. For N2 = 0.8 atm/1610 atmkgH₂O/mol. 40m below sea level, P = 6 atm. What is the concentration of O2 and N2?