A man can row his boat with the stream at 8 km/h and against the stream in 4 km/h. The man's rate is?	Pick one
A) 1 kmph	B) 2 kmph	C) 8 kmph	D) 7 kmph	E) 5 kmph

Rationale: "ds = 8 us = 4 s = ? s = ( 8 - 4 ) / 2 = 2 kmph answer : b"
Answer: B