A boat goes 130 km downstream in 10 hours, and 75 Km upstream in 15 hours. The speed of the stream is?  Select the correct option.
A) 3.5	B) 3	C) 5	D) 4	E) 8
125 --- 10 DS = 130   ? ---- 1   75 ---- 15 US = 5   ? ----- 1 S = (13 - 5)/2= 
<gadget id="calculator">(13 - 5)/2</gadget>
<output>4</output>
4 kmph.   Answer:4
<result>D</result>
A boat goes 130 km downstream in 10 hours, and 75 Km upstream in 15 hours. The speed of the stream is?