An open vertical tank contains two immiscible liquids: an oil floating on a water layer. The tank bottom is taken as the elevation $z = 0$ m. The water layer is 1.0 m deep (density of water $\rho_w = 1000\ \mathrm{kg\,m^{-3}}$). Above the water there is a layer of oil of 1.0 m depth. The relative density of the oil with respect to water is $RD_{oil} = 0.8$. The tank is open to the atmosphere, so the free surface is at atmospheric pressure. Take the atmospheric pressure as $p_{atm} = 101\,300$ Pa and $g = 9.81\ \mathrm{m\,s^{-2}}$.

Two vertical, transparent tubes (piezometers) are connected to the tank, as shown in Fig. Q1-1 (see the paper). One piezometer is connected to the tank wall at an elevation of $z = 1.5$ m above the bottom, and the other at an elevation of $z = 0.5$ m.