So the first step is to realize that air is composed approximately 79% nitrogen and approximately 21% oxygen. Now, this translates to zero 79 mole fraction nitrogen and 0.2 1 mol fraction of oxygen. So the first step is to use rolled slow. But before we use a roll slow, we must assume that there is dynamic equilibriums between the gas molecules in the space above and the gas molecules dissolved within our blood. So let's make that assumption. Now, we can find the partial pressures of each gas by simply using the formula.