a$)$ Assume that the leaf is in the closed position. The mass of the leaf is $10,000$ kg and the center of

gravity is $8$ m to the left of the trunnion bearing $($the pivot point$).$ The live load bearing support at the left

end of the leaf is $20$ m from the trunnion bearing, the rear break in the deck is $2$ m from the trunnion

bearing and the center of gravity of the counterweight $($CWT$)$ is $4$ m from the trunnion bearing. What is

the mass of the counterweight that should be specified to balance the leaf and make the bridge as easy to

open as possible?