A shaft alley divides a vessel's cargo hold into two tanks, each 25 ft. wide by 50 ft. long. Each tank is filled with salt water below the level of the shaft alley. The vessel's displacement is 6,000 tons. What is the reduction in GM due to free surface effect?

Correct Answer: Option C — .62 foot

A shaft alley divides the space into two separate 25'x50' tanks, reducing the individual breadth cubed factor. Calculating the combined free surface effect for both spaces on a 6,000-ton displacement vessel in saltwater yields a 0.62 foot GM reduction.