A U-tube manometer is connected to a closed tank shown below, containing oil with a density of 850 kg/m^3. The pressure of the air above the oil is 3200 Pa. If the pressure at point A in the oil is 18000 Pa and the manometer fluid has a density of 2800 kg/m^3, determine:
1. The depth of oil, z1
2. The differential reading, z2, on the manometer