The C.P of 30 books is equal to the S.P of 40 books. Find his gain% or loss%?
Choose the correct choice from the following answers:
A) 23 %
B) 24 %
C) 25 %
D) 50 %
E) 40 %

Rationale: "explanation : 30 cp = 40 sp 40 - - - 10 cp loss 100 - - - ? = > 25 % loss answer : c"
Answer: C