4. The water in a tank is pressurized by air, and the pressure is measured by a multi-fluid manometer as shown in Figure 2. Determine the gage pressure of air in the tank if h₁ = 0.2 m, h2 = 0.3 m, and h3 = 0.4 m. Take the densities of water, oil, and mercury to be 1000 kg/m³, 850 kg/m³, and 13,600 kg/m³, respectively. Air 1 Oil Water h3 Mercury Figure 2 Sketch of problem 4 2