\({\mathrm{I}=\frac{\text { Magnetic moment }}{\text { Volume }}}\)
\({\mathrm{I}=\frac{20 \times 10^{-6}}{10^{-6}}=20\, \mathrm{N} / \mathrm{m}^{2}}\)
\({x=\frac{20}{60 \times 10^{3}}=\frac{1}{3} \times 10^{-3}}\)
\({=0.33 \times 10^{-3}=3.3 \times 10^{-4}}\)