From a uniform wire, two circular loops are made (i) $P$ of radius $'r'$ and (ii) $Q$ of radius $nr$. If the moment of inertia of $Q$about an axis passing through its centre and perpendicular to its plane is 8 times that of $P$ about a similar axis, the value of $'n$ is (diameter of the wire is very much smaller than $i$ or $nr$ ) :
