The cost price of an article is 70% of the marked price. Calculate the gain percent after allowing a discount of 10%.
Choose the correct choice from the following choices:  A) 13.6 %  B) 28.6 %  C) 35.6 %  D) 42.3 %  E) none

Rationale: "sol . let marked price = rs . 100 . then , c . p . = rs . 70 . s . p = rs . 90 . â ˆ ´ gain % = [ 20 / 70 * 100 ] % = 28.6 % . answer b"
Answer: B