380. A 7,000 ton displacement tankship carries two slack tanks of alcohol with a S.G. of 0.8. Each tank is 50 ft. long and 30 ft. wide. What is the reduction in GM due to free surface with the vessel floating in sea water, S.G. is 1.026?

The reduction in GM due to free surface is calculated by summing the free surface moments of all slack tanks, multiplying by the liquid-to-water specific gravity ratio, and dividing by the ship's volume displacement, resulting in a reduction of 0.72 ft.