A man sells an article at a profit of 25%. If he had bought it at 20% less and sold it for Rs.16.80 less, he would have gained 30%. Find the cost of the article.
Choose the correct choice from the following answers:
A) 30 B) 40 C) 50 D) 60 E) 80

Rationale: "let c . p = 100 gain = 25 % s . p = 125 supposed c . p = 80 gain = 30 % s . p = ( 130 * 80 ) / 100 = 104 diff = ( 125 - 104 ) = 21 diff 21 when c . p = 100 then diff 16.80 when c . p = ( 100 * 16.80 ) / 21 = 50 answer : e"
Answer: E