In a river flowing at 2 km/hr, a boat travels 64 km upstream and then returns downstream to the starting point. If its speed in still water be 6 km/hr, find the total journey time. Choose the correct option:	A) 10 hours	B) 12 hours	C) 14 hours	D) 24 hours	E) none of these

Rationale: "explanation : speed of the boat = 6 km / hr speed downstream = ( 6 + 2 ) = 8 km / hr speed upstream = ( 6 - 2 ) = 4 km / hr distance travelled downstream = distance travelled upstream = 64 km total time taken = time taken downstream + time taken upstream = ( 64 / 8 ) + ( 64 / 4 ) = = 24 hr . answer : option d"
Answer: D