A person sells a book for Rs. 11. He gains as many percent as its cost price in rupees. What is the cost price?  Choices:
A) Rs. 19  B) Rs. 12  C) Rs. 10  D) Rs. 11  E) Rs. 14
ANSWER: Rs. 10
<result>C</result>
A person sells a book for Rs. 11. He gains as many percent as its cost price in rupees. What is the cost price?