4. A vessel contains oil

(density = 0.8 gm/cm³) over mercury (density = 13.6 gm/cm³). A homogeneous sphere floats with half of its volume immersed in mercury and the other half in oil. The density of the material of the sphere in gm/cm³ is

(a)  3.3                                      (b)   6.4

(c)   7.2                                      (d)  12.8

Answer-c

(41)