A boat running downstream covers a distance of 12 km in 2 hours while for covering the same distance upstream, it takes 3 hours. What is the speed of the boat in still water?  Options: A) 8 kmph B) 5 kmph C) 4 kmph D) 6 kmph E) 7 kmph

Rationale: "speed downstream = 12 / 2 = 6 kmph speed upstream = 12 / 3 = 4 kmph speed of the boat in still water = 6 + 4 / 2 = 5 kmph answer : b"
Answer: B