On a vessel of 6500 tons displacement, a tank 30 ft. long, 32 ft. wide and 15 ft. deep is half filled with oil cargo (S.G. 0.948) while the vessel is floating in saltwater (S.G. 1.026). What is the free surface constant for this tank?

Correct Answer: Option D — 2162

Free surface constant calculation incorporates tank length and cubed breadth divided by 12, then adjusted for cargo and saltwater specific gravities (SG 0.948 / 1.026). For a 30x32x15 ft tank, this yields 2162.