A dishonest dealer professes to sell goods at the cost price but uses a weight of 600 grams per kg, what is his percent?  Choose the correct choice from the following:
A) 28 %
B) 66.7 %
C) 55 %
D) 28 %
E) 55 %

Rationale: "600 - - - 400 100 - - - ? = > 66.7 % answer : b"
Answer: B