There is a gaseous solution of CO2 and O2. The temperature is 60,3 °C, and the pressure is 2,0 atm. If the density of the solution is 3,0 g/L, what is the percentage of O2 (in volume)?

Could you guys give me a hint on how to solve this exercise? I know that d = (P.M) / (R.T), and I found that the total mass is 41g, but I'm really totally lost here.

Thanks