A passenger train leaves station A at 06:00 h and reaches station B at 09:20 h after covering 220km on a straight track. Later the same day, the train makes the return trip from B to A, covering the same 220km in 3h40min.
(a) Find the average speed of the train on the journey from A to B in km/h.
(b) Express this speed in m/s.
(c) Calculate the average speed on the return journey from B to A in km/h.
(d) Determine the overall average speed of the train for the complete round trip.