The liquid mud tanks on your vessel measure 40'L by 20'B by 8'D. The vessel's displacement is 996 T and the specific gravity of the mud is 1.7. What is the reduction in GM due to a pair of these tanks (p/s) being slack?

Correct Answer: Option D — 2.54 feet

Free surface effect (FSE) reduces initial transverse stability by lowering effective GM. Calculated using the formula FSM = (Length × Breadth³ × SG of liquid) / 12, then dividing the total free surface moment by vessel displacement (996 T). Summing effects for a P/S pair of tanks yields a 2.54-foot reduction in GM.