Suppose you have a system of two masses strung over a pulley. Mass 1 (7 kg) hangs on the right side of the pulley suspended over the ground at height 1.1 m. Mass 2 (2.9 kg) hangs over the left side of the pulley and rests on the ground. The pulley is a uniform disk of mass m and radius 12.2 cm. When the system is released, Mass 1 moves down and Mass 2 moves up, such that Mass 1 strikes the ground with speed 1.1 m/s. This is called an Atwood Machine. Calculate the mass of the pulley in kg.