A 2.5-L fl ask at 15C contains a mixture of N2, He, and Ne at partial pressures

Question:

A 2.5-L fl ask at 15°C contains a mixture of N2, He, and Ne at partial pressures of 0.32 atm for N2, 0.15 atm for He, and 0.42 atm for Ne.
(a) Calculate the total pressure of the mixture.
(b) Calculate the volume in liters at STP occupied by He and Ne if the N2 is removed selectively.