On a vessel of 6500 tons displacement, a tank 35 ft. long, 25 ft. wide, and 8 ft. deep is half filled with liquid cargo (S.G. 1.053) while the vessel is floating in saltwater (S.G. 1.026). What is the free surface constant for this tank?

Correct Answer: Option B — 1,336

Free surface effect on stability is proportional to the moment of inertia of the tank waterplane and the specific gravity ratio. For a 35x25 ft tank with liquid SG 1.053 in saltwater, the computed constant equals 1,336.