A rigid tank shown in Fig. 1, initially under atmospheric pressure, contains oil (poil 850 kg/m') and water (Pwater = 1000 kg/m'). Air is then charged into the tank to increase the total pressure up to l MPa gage. Determine the total downward movement of the free surface of the oil. Take average values of elastic bulk modulus for oil and water as 2050 MPa and 2075 MPa, respectively. Air 200 mm Oil 600 mm Water 700 mm 300 mm Fig. 1