Rotational Motion

A thin uniform circular disc of mass '\(\mathrm{M}\)' and radius '\(R\)' is rotating with angular velocity '\(\omega\)', in a horizontal plane about an axis passing through its centre and perpendicular to its plane. Another disc of same radius but of mass \(\left(\frac{M}{2}\right)\) is placed gently on the first disc co-axially. The new angular velocity will be