What is the moment of inertia of a solid sphere of radius $R$ and density $\rho$ about its diameter?

Two rods,each of mass $m$ and length $l$,are joined at their centers to form a cross. What is the moment of inertia of the cross about an axis passing through their common center and perpendicular to the plane of the rods?

$A$ thin uniform rod of length $L$ and mass $M$ is bent at the middle point $O$ at an angle of $45^{\circ}$ as shown in the figure. The moment of inertia of the system about an axis passing through $O$ and perpendicular to the plane of the bent rod is:

$A$ circular disc of radius $b$ has a hole of radius $a$ at its centre (see figure). If the mass per unit area of the disc varies as $\sigma(r) = \frac{\sigma_0}{r}$,then the radius of gyration of the disc about its axis passing through the centre is

The ratio of radii of gyration of a ring to a disc (both circular) of same radii and mass,about a tangential axis perpendicular to the plane is

Point masses $1, 2, 3$ and $4 \text{ kg}$ are lying at the points $(0,0,0), (2,0,0), (0,3,0)$ and $(-2,-2,0)$ respectively. The moment of inertia of this system about the $x$-axis will be: