The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown in Fig. P1-50. Determine the gage pressure of air in the tank if $h_{1}=0.2 \mathrm{m}, h_{2}=0.3 \mathrm{m},$ and $h_{3}=0.4 \mathrm{m} .$ Take the densities of water, oil, and mercury to be $1000 \mathrm{kg} / \mathrm{m}^{3}, 850 \mathrm{kg} / \mathrm{m}^{3},$ and $13,600 \mathrm{kg} / \mathrm{m}^{3},$ respectively.