$5 \text{ litres}$ of benzene weighs

Three different liquids are filled in a $U$-tube as shown in the figure. Their densities are $\rho_1, \rho_2$ and $\rho_3$ respectively. From the figure,we may conclude that:

$A$ tank $5 \,m$ high is half filled with water and then is filled to the top with oil of density $0.85 \,g/cm^3$. The pressure at the bottom of the tank,due to these liquids is ........ $g/cm^2$.

$A$ nurse measures the blood pressure of a seated patient to be $190 \,mm$ of $Hg$.

$A$ $U$ tube contains water and methylated spirit separated by mercury. The mercury columns in the two arms are at the same level with $10\,cm$ of water in one arm and $12.5\,cm$ of spirit in the other,as shown in the figure. The relative density of the spirit is

$A$ bubble from the bottom of a lake rises to its surface. Its volume doubles in the process. Assuming isothermal conditions, atmospheric pressure $= 75 \, cm$ of $Hg$, and the ratio of the densities of mercury and water $= 40/3$. The depth of the lake will be ..... $m$.