“…13 , w 13 , v 12 , w 12 , x 2 , y 2 , z 2 } and f B (s) � 0 if s ∈ c, y 3 , z 3 , w 23 , v 23 }. e set A contains a subset A ′ , with |A ′ | � 3, T A′ (s) ≥ (1/2) for s ∈ u 12 , v13 , w 13 , and each edge in A ′ has one end at x 2 . Note that T A′ (c) ≤ (1/2), either T A′ (w 23 ) � 0 or T A′ (w 12 ) � 0, and eitherT A′ (v 12 ) � 0 or T A′ (v 23 ) � 0.…”