Moment of Inertia

I have a homework question that i simply can't get my head around, and it's driving me nuts, any help would be greatly appreciated,

The question wants me to calculate the moment of inertia for a thin disk radius b with uniform density p, that lies in the x-y plane.

But it wants me to find the moment of inertia about the x axis, using polar co ordinates.

I have worked this out using perp. axis thm but i'm not allowed to use that here, have to calculate from scratch.

thanks for any help.

It's ok, worked it out was simply stuffing up the integration, and thought i was further off than i was.