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 km/h and the speed of the boat in still water is 14 km/h, what is the distance between A and B? Choices
A) 200 km  B) 180 km  C) 160 km  D) 220 km  E) none of these

Rationale: "speed of boat for downstream = 14 + 4 = 18 km / hr speed of boat for upstream = 14 – 4 = 10 km / hr distance = x x / 18 + ( x / 2 ) / 10 = 19 x = 180 km answer : b"
Answer: B