premise: Exactly five volunteers—Haddad, Joslin, Kwon, Molina, and Nash—are being assigned to three community committees—X, Y, and Z. Each committee will have three volunteers assigned to it, with each volunteer on a committee holding exactly one of three positions—leader, secretary, or treasurer. The following conditions apply: If Nash is assigned to a committee, Nash must be the leader for that committee. Molina must be assigned to exactly one committee. Kwon must be assigned to Y but cannot be assigned to Z. Joslin must be the secretary for Y but cannot be assigned to X or Z. If Kwon is assigned to be leader for exactly one of the committees, then for which of the committees is the assignment of volunteers to positions fully determined?
hypothesis: X and Y, but not Z