pls solve the b part …..

The charges rearrange in such a manner that inside the cavity the electric field is zero. Now since there is a charge at the centre which is +q, The charge on the inner side of the inner shell is -q and hence on the outer side will be +3q so as to give 2q total and similarly the inner side of the outer shell will be -3q and therefore on the outer side will be +6q and hence the inner electric field will be zero and the outer one will beaccording to 6q charge.