Two identical cylindrical vessels with their bases at same level each contains a liquid of density r. The height of the liquid in one vessel is \[{{h}_{1}}\] and that in the other vessel is \[{{h}_{2}}\]. The area of either base is A. The work done by gravity in equalizing the levels when the two vessels are connected, is [SCRA 1996]

• A.        \[({{h}_{1}}-{{h}_{2}})g\rho \]
• B.        \[({{h}_{1}}-{{h}_{2}})gA\rho \]
• C.        \[\frac{1}{2}{{({{h}_{1}}-{{h}_{2}})}^{2}}gA\rho \]
• D.        \[\frac{1}{4}{{({{h}_{1}}-{{h}_{2}})}^{2}}gA\rho \]