The C.P of 5 pens is equal to the S.P of 7 pens. Find his gain % or loss%?	Choose the correct answer
A) 25 4/7%	B) 26 4/7%	C) 28 4/7%	D) 14 4/7%	E) 23 4/7%
528 4/7%P = 7 SP   7 --- 2 28 4/7%P loss   100 --- ? =&gt; 28 4/7%   Answer: 28 4/7%
<result>C</result>
The C.P of 5 pens is equal to the S.P of 7 pens. Find his gain % or loss%?