PHY$111$ Test $3$ on Rotational Motion

A flywheel at the bottom rotates without friction at an angular velocity ${}_0=600re\frac{v}{m}in$ on a frictionless, vertical shaft of negligible rotational inertia. A second flywheel, which is at rest and has a moment of inertia three times that of the rotating flywheel, is dropped onto it$.$ The flywheels very quickly reach the same rotational velocity after which they spin together. Use the law of conservation of angular momentum to determine the angular velocity $$ of the combination. $($Please show your work$)$