A small uncharged conducting sphere is placed in contact with an identical sphere but having 4 × 10^–8 C charge and then removed to a distance such that the force of repulsion between them is 9 × 10^–3 N. The distance between them is (Take \(\frac{1}{4 \pi \varepsilon_{0}}\) as 9 × 10⁹ in SI units)