The C.P of 20 pens is equal to the S.P of 12 pens. Find his gain % or loss%?	Choose the correct choice: A) 10 % B) 20 % C) 30 % D) 40 % E) 50 %

Rationale: "20 cp = 12 sp 20 - - - 8 cpgain 100 - - - ? = > 40 % answer : d"
Answer: D