If an article is sold at 18% profit instead of 9% profit, then the profit would be $72 more. What is the cost price?
Answers:	A) $ 500	B) $ 600	C) $ 700	D) $ 800	E) $ 900

Rationale: "9 % * cost price = $ 72 1 % * cost price = $ 72 / 9 = $ 8 the cost price is $ 800 . the answer is d ."
Answer: D