Capital gains on redevelopment property

I had 3 flats with 500 Sq ft each worth 20 lakhs in mumbai purchased in march 2005, In Sep 2009 the building went into redevelopment and was granted 3 flats with 750 sq ft each by builder In Feb 2012 I sold all the 3 flats 60 lakhs each what should be the capital gains and cost of acquistions for the same