1. The problem statement, all variables and given/known data 2. Relevant equations GPE=mgh 3. The attempt at a solution I don't understand why the answer is B. My approach is assigning h a random value, say 10m. When the depths of water in both vessels are equal, the height is 5m. Therefore, since the mass of water in both vessels are still m, shouldn't the loss in GPE be half? I don't know why I'm wrong.