A mass m1 = 16.0 kg is connected by a light string that passes over a pulley of mass M = 11.5 kg to a mass m2 = 6.00 kg sliding on an inclined frictionless surface that makes an angle of 28° with the horizontal (see figure). There is no slippage between the string and the pulley. What is the magnitude of the acceleration of the system of masses? (The moment of inertia of the pulley is 1/2Mr².)