A horizontal platform in the shape of a circular disk rotates on a frictionless bearing about a vertical axle through the centre of the disk. The platform has a mass of `150 kg`, a radius of `2.0 m`, and a rotational inertia of`300 kg m^2` about the axis of rotation. A `60 kg` student walks slowly from the rim of the platform toward the centre. If the angular speed of the system is `1.5 rad//s` when the student starts at the rim, what is the angular speed when she is `0.50 m` from the centre ?