Rotational Dynamics

Hey, I've gotten stuck with this question: https://i.gyazo.com/bd6530d77639c6b556d78737c6a7f6ee.png

So basically, for (i) I'm going to assume this is based on the conservation of angular momentum/torque.

(ii) Since w_s/w_w = I_w/I_s then w_s = I_w/I_s * w_w

(iii) This is the one which has gotten me stuck the most, we're only given the combined moment of inertia, what else could one use?

(iv) No need to help for this, I'm mainly wondering about (ii) and (iii).

Thanks!