What will be my Capital gains tax liability for a flat sold for Rs 21.5 lakhs on June'2011 ?

The flat was built on a land gifted to me by my grandfather on April'2002 which is hereditary and whose cost price I could not find out as early as 1947.The multistoried building was constructed by a reputed Developer who started building on October'2007 and after building I resided in one flat and sold the other on June '2011.