“…Nodes in (a) can be divided into V 1 = {1, 2, 3}, V 2 = {4, 5, 6} and all the negative edges are between different sets. The nodes in (b) (i.e., the edges in (a)) can be divided into E 1 = {(1, 2), (2, 3), (4, 2), (5, 2), (6, 1)} and E 2 = {(2, 6), (3,4), (4,5), (5,6)}. Thus (a) is structurally balanced.…”