Two cylindrical vessels of equal cross-sectional area $16 \mathrm{~cm}^{2} contain water upto heights 100 \mathrm{~cm} and 150 \mathrm{~cm} respectively. The vessels are interconnected so that the water levels in them become equal. The work done by the force of gravity during the process, is [Take, density of water =10^{3} \mathrm{~kg} / \mathrm{m}^{3} and \mathrm{g}=10 \mathrm{~ms}^{-2}$ ] :