dA < dF
dA > dF
dB > dF
dA + dB = 2dF
For sphere A to be at the top in liquid, the density of sphere A should be less than the density of liquid. And for sphere B to be at the bottom in liquid, the density of sphere B should be greater than the density of the liquid. The FBD of the top sphere gives us VdFg = T + VdAg and of the bottom sphere gives us T + VdFg = VdBg Substituting T from the first equation in the second we get 2VdFg = VdAg + VdBg or 2dF = dA + dB