A gas mixture contains each of the following gases at the indicated partial pressures: $\mathrm{N}_{2}, 215$ torr; $\mathrm{O}_{2}, 102$ torr; and He, 117 torr. What is the total pressure of the mixture? What mass of each gas is present in a 1.35 L sample of this mixture at $25.0^{\circ} \mathrm{C} ?$