An epicyclic gear train is shown in the figure below. Gears D - E and F - G are compound gears. D gears with A and B; E gears with F; and G gears with C. The numbers of teeth or each gears are A = 60, B = 120, C = 135, D = 30, E = 75, F = 30, G = 60. If the wheel A is fixed and the arm makes 20 revolutions clockwise, find the revolution of gear C.