A man can row his boat with the stream at 6 km/h and against the stream in 4 km/h. The man's rate is?	Pick one:
A) 1  B) 2  C) 3  D) 5  E) 7

Rationale: "ds = 6 us = 4 s = ? s = ( 6 - 4 ) / 2 = 1 kmph answer : a"
Answer: A