$\begin{align}  & {{P}_{A}}={{P}_{B}} \\  & {{P}_{^{0}}}+{{P}_{1}}gh={{P}_{^{0}}}+{{P}_{1}}gh\to 1500\times 6={{\rho }_{2}}\times 9 \\  & {{\rho }_{2}}=\frac{1500\times 6}{9}=1000 \\ \end{align}$