57. Determine the free surface constant for a fuel oil tank 30 ft. long by 40 ft. wide by 15 ft. deep. The specific gravity of the fuel oil is .85 and the ship is floating in saltwater (S.G. 1.026).

The free surface constant for a rectangular fuel oil tank is calculated using the tank's length and breadth, adjusted by the ratio of the fuel oil's specific gravity to that of saltwater. The formula involves the second moment of area and a conversion factor to express the result in ft-tons, yielding a value of 3787.