A man can row his boat with the stream at 18 km/h and against the stream in 4 km/h. The man's rate is?  Choose the correct choice from the following choices:
A) 1 kmph B) 3 kmph C) 8 kmph D) 7 kmph E) 5 kmph
7 kmphS = 18   US = 4   S = ?   S = (18 - 4)/2= 
<gadget id="calculator">(18 - 4)/2</gadget>
<output>7</output>
7 kmph   Answer: 7 kmph
<result>D</result>
A man can row his boat with the stream at 18 km/h and against the stream in 4 km/h. The man's rate is?