Mixtures of helium and oxygen are used in scuba diving tanks to help prevent "the bends". For a particular dive, 18.9 L of oxygen gas at 25.0oC and 1.25 atm, and 7.58 L of helium gas at 25.0oC and 1.13 atm were pumped into a tank with a volume of 6.00 L at 25.0oC. Calculate (in atm): 1. the partial pressure of oxygen 2. the partial pressure of helium 3. the total pressure in the tank at 25.0oC.