The figure shows two solid discs with radius $$R$$ and $$r$$ respectively. If mass per unit area is the same for both, what is the ratio of MI of bigger disc around axis $$AB$$ (Which is $$\perp$$ to the plane of the disc and passing through its centre) of MI of smaller disc around one of its diameters lying on its plane? Given $$M$$ is the mass of the larger disc.

A

$$R^2 : r^2$$

B

$$2r^4 : R^4$$

C

$$2R^2 : r^2$$

D

$$2R^4 : r^4$$