Figure shows a man of mass 50kg standing on a light weighing machine kept in a box of mass 30kg. The box is hanging from a pulley fixed to the ceiling through a light rope, the other end of which is held by the man himself. If the man manages to keep the box at rest, the weight shown by the machine is _______ N.
(A) 100N
(B) 150N
(C) 200N
(D) 50N
