Thank you for reporting, we will resolve it shortly
Q.
In the above question, $B$ and the magnetising current is
Magnetism and Matter
Solution:
The magnetising current $I_{m}$ is the additional current that needs to be passed through the windings of the solenoid in the absence of the core which would given a $B$ value as in the presence of the core.
Thus, $B=\mu_{r} n_{0}\left(I+I_{m}\right)$
using $I=2\, A , B=1\, T$,
we get $I_{m}=794\, A$