They have provided insufficient information to answer this question. This would either be a long question, or a passage. Either way, as it is now, it is not MCAT-esque.
This three-valve system with a spinning chamber has been used for more than one kind of experiment, so unless they specify what they are doing, you are left with assuming different possibilities, and they all have different possible answers.
I'm surprised this is from TBR. They are usually accurate and specific to a fault.