An iron rod of susceptibility 599 is subjected to a magnetising field of 1200 Am-1. The permeability of the material of the rod is :
1. 8.0 x10⁻⁵ T m A⁻¹
2. 2.4π × 10⁻⁵ T m A⁻¹
3. 2.4π × 10⁻⁷ T m A⁻¹
4. 2.4π × 10⁻⁴ T m A⁻¹