A large vessel with a small hole at the bottom is filled with water and kerosine with kerosine floating on water. The length of water column is $20 \mathrm{~cm}$ and that of kerosine is $25 \mathrm{~cm}$. The velocity with which water flows out of the hole is (density of kerosine $=0.8 \mathrm{~g} \mathrm{~cm}^{-3}$, neglect viscous force).