A 20 L tank of oxygen has a pressure of 0.30 atm and a temperature of 300 K. A 30 L tank of nitrogen has a pressure of 0.60 atm and a temperature of 300 K. The oxygen is transferred to the nitrogen tank where the two mix. What is the pressure of the mixture if its temperature stays at 300 K?
a. 0.70 atm
b. 0.75 atm
c. 0.78 atm
d. 0.80 atm
e. 0.90 atm