A frictionless pulley has the shape of a uniform solid disk of mass 4.00 kg and radius 28.0 cm. A 3.90 kg stone is attached to a very light wire that is wrapped around the rim of the pulley , and the stone is released from rest. As it falls down, the wire unwinds without stretching or slipping, causing the pulley to rotate. How far must the stone fall so that the pulley has 2.70 J of kinetic energy?