A mass of 8 kg is resting on a horizontal table with a coefficient of kinetic friction of 0.35. The mass is connected to a cable that passes over a pulley of mass 3.5 kg and radius 21 cm. The other end of the cable is attached to a second hanging mass of 15 kg. The system is released from rest.
(a) Calculate the linear acceleration of the system.
(b) How many times does the pulley rotate in 2 seconds?