A cylindrical bucket of negligible mass has radius R and height h, and is open at the top. It is submerged in water of density \rho, with its top a distance H below the surface. How much work is needed to pull the bucket slowly up so that its bottom is just above the lake surface?
Answer Choices
A. \rho g \pi R^{2} h(H-h)
B. \rho g \pi R^{2} h^{2}
C. \rho g \pi R^{2}(H-h)^{2}
D. \rho g \pi R^{2} h^{2} / 2 \leftarrow CORRECT
E. \rho g \pi R^{2} h(H-h) / 2
