A boat takes 38 hours for travelling downstream from point A to point B and coming back to point C midway between A and B. If the velocity of the stream is 4 kmph and the speed of the boat in still water is 14 kmph, what is the distance between A and B?
Choose the correct choice from the following options:  A) 240 km  B) 120 km  C) 360 km  D) 180 km  E) none of these

Rationale: "explanation : velocity of the stream = 4 kmph speed of the boat in still water is 14 kmph speed downstream = ( 14 + 4 ) = 18 kmph speed upstream = ( 14 - 4 ) = 10 kmph let the distance between a and b be x km time taken to travel downstream from a to b + time taken to travel upstream from b to c ( mid of a and b ) = 38 hours ⇒ x / 18 + ( x / 2 ) 10 = 38 ⇒ x / 18 + x / 20 = 38 ⇒ 19 x / 180 = 38 ⇒ x / 180 = 2 ⇒ x = 360 i . e . , the distance between a and b = 360 km . answer : option c"
Answer: C