Define retentivity, coercivity and hysteresis loss. Why soft iron is used in the core of a transformer?

The magnetic field induction in a material placed in a magnetising field of $2000{\mathrm{Am}}^{-1}$ is $1.0 \mathrm{N} {\mathrm{A}}^{-1} {\mathrm{m}}^{-1}$. Find magnetic permeability.

The magnetic field induction in a material placed in a magnetising field of $2000{\mathrm{Am}}^{-1}$ is $1.0 \mathrm{N} {\mathrm{A}}^{-1} {\mathrm{m}}^{-1}$. Find relative permeability.

The magnetic field induction in a material placed in a magnetising field of $2000{\mathrm{Am}}^{-1}$ is $1.0 \mathrm{N} {\mathrm{A}}^{-1} {\mathrm{m}}^{-1}$. Find magnetic susceptibility and  ${\mu }_0=4\pi \times {10}^{-7} \mathrm{N} {\mathrm{A}}^{-2}$. 

The magnetic field induction in a material placed in a magnetising field of $2000{\mathrm{Am}}^{-1}$ is $1.0 \mathrm{N} {\mathrm{A}}^{-1} {\mathrm{m}}^{-1}$. Find intensity of magnetisation for the material.