Two discs of moment of inertia ${\text{I}}_{\text{1}}$ and  ${\text{I}}_2$ and angular speed  ${\text{ω}}_{\text{1}}$ and  ${\text{ω}}_2$ are rotating in the same direction along collinear axes passing through their c.m. and perpendicular to their plane. If the two are made to rotate combinedly along the same axis, the final rotational KE of system when they rotate together with same angular velocity is