Asked by Dug

Three objects with masses m1 = 7.4 kg, m2 = 11 kg, and m3 = 18 kg, respectively, are attached by strings over frictionless pulleys (M1 hangs off the left side of the table and M3 hangs off the right side of the table with M2 between them on the table). The horizontal surface exerts a force of friction of 30 N on m2. If the system is released from rest, use energy concepts to find the speed of m3 after it moves down 4.0 m.
I don't have a CLUE where to start....