If the cost price is 90% of the selling price, then what is the profit percent? Select the correct option.
A) 5 %
B) 11 %
C) 13 %
D) 21 %
E) 19 %

Rationale: "let s . p . = $ 100 c . p . = $ 90 profit = $ 10 profit % = 10 / 90 * 100 = 25 / 6 = 11 % approximately answer is b"
Answer: B