If we were to increase atmospheric CO2 fivefold by the burning of fossil fuels, how much would the atmospheric oxygen concentration change relative to what it is today? Assume: (a) CO2 concentration today is 400 ppm, (b) the atmosphere today is made of 21% oxygen, and (c) the burning of fossil fuels consumes 1.4 moles of O2 per mole of CO2 produced