I believe the answer is: Nicole as the timekeeper, Rahul as the facilitator, and Marina as the notetaker.
Timekeeper has to be able to maintain the course of group study so it does not resorted to other unrelated activities.
Facilitator need to play the central role that give direction in the group study, so being respected and well liked is important. Not takers need to have high attention in detail and able to write in a fast pace.
