Can You help me With Math?

Cross-sectional area of the pipe is pi*r^2 = 3.14159*12^2 = 3.14159*144 = 452.39 square inches. 8 feet = 96 inches, so total volume = 96 inches * 452 sq. inches = 43,392 cubic inches. 43392 cu. inches / (12*12*12 cu in per cu foot) = 43392 / 1728 = 25.11 cu. feet, so a) is the most correct answer.