A boat takes 19 hours for travelling downstream from point A to point B and coming back to a 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 ?	Select
A) 160 km  B) 180 km  C) 200 km  D) 220 km  E) 240 km

Rationale: down stream speed : ( 14 + 4 ) km / hr = 18 km / hr up stream speed : ( 14 - 4 ) km / hr = 10 km / hr ( x / 18 ) + ( x / 2 / 20 ) = 19 x = 180 km answer : b
Answer: B