A U-tube is open to the atmosphere at both ends. Water is poured into the tube until the water rises part-way along the straight sides, and then some oil with a density of 920 kg/m^3 is poured into one end. This causes the water surface on that side of the tube to go down by 5.50 mm, and the surface on the other side to go up by the same amount. How much higher is the top surface of the oil on that side of the tube compared with the surface of the water on the other side of that tube?