A person can swim in still water at 4 km/h. If the speed of water 2 km/h, how many hours will the man take to swim back against the current for 8km?
Choose the correct choice from the following answers:
A) 4  B) 7  C) 8  D) 9  E) 6

Rationale: "m = 4 s = 2 us = 4 - 2 = 2 d = 8 t = 8 / 2 = 4 answer : a"
Answer: A