The liquid mud tanks on your vessel measure 24'L by 16'B by 8'D. The vessel's displacement in salt water (specific gravity 1.025) is 864 T and the specific gravity of the mud is 1.47. What is the reduction in GM due to a pair of these tanks (p/s) being slack?

Correct Answer: Option B — 0.78 foot

Free surface correction (FSC) equals total free surface moments divided by vessel displacement (864 T). Multiplying tank dimensions and mud specific gravity (1.47) through the standard inertial formula (L³B or LB³/12 depending on axis) for P/S liquid mud tanks dictates a net 0.78-foot decrease in metacentric height.