I don't read much IPO research documents from broker firms but glanced through this one. The best practice is to take off one off gains and "Normalise" earnings in calculating P/E ratios. As per the research document, P/E ratio is 20.37 based on 2011 earnings. However, if we eliminate this irregular gain, P/E ratio would be 29 times.
refer page number 109 in the prospectus (4th line item in the income statement).