A marine shellfish must locally maintain to precipitate calcium carbonate CaCO₃ under two conditions of equilibrium: a preindustrial atmosphere containing approximately 280 ppm CO₂ or a modern atmosphere containing approximately 400 CO₂. Ocean water has pH around 8. Calculate the concentration of CO₂aq in (mol/liter) under the equilibrium condition of a modern atmosphere containing approximately C(air)= 450 ppm CO₂. (Keep two significant figures)