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 6x km.	Choose the correct choice from the following options.
A) 40 kmph	B) 45 kmph	C) 48 kmph	D) 50 kmph	E) 55 kmph

Rationale: "total time taken = x / 40 + 2 x / 20 hours = 5 x / 40 = x / 8 hours average speed = 6 x / ( x / 8 ) = 48 kmph answer : c"
Answer: C