Three Bulbs Are Connected as Shown in the Diagram Below

Three bulbs are connected as shown in the diagram below.For purposes of a biology experiment,an artificial atmosphere is being created for test animals to breathe.What is the partial pressure of oxygen inside the system when all the valves are opened and the gases mix completely? The flasks are at the same temperature,and the temperature does not change when the gases mix.Assume the volume of the tube connecting the bulbs is negligible.