An iron rod is placed parallel to magnetic field of intensity $2000 \mathrm{A} \mathrm{m}$. The magnetic flux through the rod is $6\times {10}^{-4}\mathrm{ Wb}$ and its cross-sectional area is $\mathrm{3 }\mathrm{c}{\mathrm{m}}^2$. The magnetic permeability of the rod in $\mathrm{W}\mathrm{b} {\mathrm{A}}^{-1}{\mathrm{m}}^{-1}$ is