Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Q: Problem: boy sells a book for rs. 540 he gets a loss of 10 %, to gain 10 %, what should be the sp ?
Options: a. 430, b. 450, c. 550, d. 590, e. 660
A:
e