Mathematics · Rotational Motion - Energy Conservation

A flywheel (disc) having mass 3 kg and radius 5 m is free to rotate about a horizontal axis. A string having negligible mass is wound around the wheel and the loose end of the string is connected to a 3 kg mass. The mass is kept at rest initially and released. What is the kinetic energy of the flywheel when the mass descends by 3 m? (Take g = 10 m/s2)