A vertical U-tube of uniform inner cross-section contains mercury in both its arms. A glycerine (rho_G = 1.3 g/cm³) column of length 10 cm is introduced into one arm. Oil (rho_o = 0.8 g/cm³) is poured into the other arm until the upper surfaces of the oil and glycerine are at the same horizontal level. Find the length of the oil column. (rho_{Hg} = 13.6 g/cm³)
