A solid cube is in equilibrium while floating in liquid mercury. It is made of iron with density $7900\,\text{kg m}^{-3}$. The cube floats with $42\%$ of its volume above the mercury surface. What is the density of the mercury?
- A$3300\,\text{kg m}^{-3}$
- B$4600\,\text{kg m}^{-3}$
- C$14\,000\,\text{kg m}^{-3}$
- D$19\,000\,\text{kg m}^{-3}$