The moment of inertia of a uniform thin rod of mass m and length l about two axis PQ and RS passing through centre of rod C and in the plane of the rod are ${\mathrm{I}}_{\mathrm{PQ}}$ and ${\mathrm{I}}_{\mathrm{RS}}$ respectively. Then ${\mathrm{I}}_{\mathrm{PQ}}+ {\mathrm{I}}_{\mathrm{RS}}$ is equal to