The figure shows the experimentally measured $B$ vs. $H$ variation in a ferromagnetic material. The retentivity,coercivity,and saturation of the material are,respectively:

Which of the following statements is incorrect about hysteresis?

The figure illustrates how $B$,the flux density,inside a sample of ferromagnetic material varies with external magnetic field $B_0$. For the sample to be suitable for making a permanent magnet,

$A$ bar magnet has a coercivity of $4 \times 10^3 \, A \, m^{-1}$. It is desired to demagnetize it by inserting it inside a solenoid $12 \, cm$ long and having $60$ turns. The current that should be sent through the solenoid is . . . . . . $A$.

The only property possessed by ferromagnetic substances is

$A$ metal rod is subjected to cycles of magnetisation at the rate of $42 \ Hz$. The density of the metal is $6 \times 10^3 \ kg \ m^{-3}$ and its specific heat capacity is $0.1 \times 10^3 \ cal \ kg^{-1} \ ^{\circ}C^{-1}$. If the area of its $B-H$ loop corresponds to an energy density of $10^{-2} \ J \ m^{-3}$,then the rise in its temperature in one minute is: (in $^{\circ} C$)