The beam is acting as the pivot and the weight of the deck acts through its center its gravity, at the midpoint of the deck.
Center of gravity at: (16 + 4)/2 = 10 ft
Converting 4 ft to meters: 1.22 m
Converting 10 ft to meters: 3.05
F x 1.22 = 3.05 x 3000 x 9.81
F = 73,600 N
