A trained covered x km at 40 kmph and another 2x km at 20 kmph. Find the average speed of the train in covering the entire 7x km.	Choose the correct choice:	A) 56	B) 18	C) 24	D) 19	E) 12

Rationale: "total time taken = x / 40 + 2 x / 20 hours = 5 x / 40 = x / 8 hours average speed = 7 x / ( x / 8 ) = 56 kmph answer : a"
Answer: A