Figure 4 shows the compound change-gear train of a centre lathe used to cut a single-start thread. Gear A turns at spindle speed; B and C are keyed to the same stud; D is on the lead screw (pitch 6 mm). The work is 24 mm in diameter, the thread length is 60 mm, the cutting speed is 9 m/min and 8 cutting passes are needed. Determine (a) the pitch of the thread cut (in mm), (b) the spindle speed (in rpm) and (c) the total cutting time for the 8 passes, neglecting return strokes (in min).