“…1, the set E R comprises 9 arcs: (1, 2), (1, 3), (3,5), (3,6), (4,5), (5, 9), (6, 5), (6, 7) and (7,9). Among them, unavoidable arcs are: (1, 2), (1,3), (3,6), (4,5), (5,9), (6,5) and (7,9). The arcs (3,5) and (6, 7) only may theoretically be deleted from the set E R if the resource allocation is modified.…”