A dishonest dealer professes to sell goods at the cost price but uses a weight of 720 grams per kg, what is his percent?
Choose the correct choice from the following
A) 15 %  B) 25 %  C) 38.9 %  D) 45 %  E) 35 %

Rationale: "explanation : 720 - - - 280 100 - - - ? = > 38.9 % answer : c"
Answer: C