If the cost price of 60 articles is equal to the selling price of 40 articles, then what is the percent profit?	Choose the correct answer: A) 30 % B) 40 % C) 50 % D) 60 % E) 70 %

Rationale: "let x be the cost price of one article . let y be the selling price of one article . 40 y = 60 x y = 1.5 x the answer is c ."
Answer: C