Lin Wanrong said with a smile, "When I went down to look for oil, I first mixed mature vinegar and oil into the pot, because the specific gravity of vinegar is greater than that of oil.". The vinegar sinks to the bottom of the pan and the oil floats on top. In this way, everyone can see that the ground and Lord Xu are scooping up oil, but they can't see vinegar. Xu Wei laughed and said, "I...