One cubic meter $\left(1.00 \mathrm{m}^{3}\right)$ of aluminum has a mass of $2.70 \times 10^{3} \mathrm{kg},$ and 1.00 $\mathrm{m}^{3}$ of iron has a mass of $7.86 \times 10^{3} \mathrm{kg}$ . Find the radius of a solid aluminum sphere that will balance a solid iron sphere of radius 2.00 $\mathrm{cm}$ on an equal-arm balance.