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 10km?  Choose the most appropriate option:
A) 3	B) 5	C) 8	D) 9	E) 6

Rationale: "m = 4 s = 2 us = 4 - 2 = 2 d = 10 t = 10 / 2 = 5 answer : b"
Answer: B