Long Term Capital Gain Tax applicable for SRA Flat

I own a flat that used to be a slum which I bought in the 90s. It was redeveloped as part of SRA in 2005. I am now planning to sell it. My question is will my cost be calculated as per inflation-adjusted ready reckoner rate of 2001 or will it be valued as being free and therefore my long-term capital gain tax be calculated at the entire sale amount being considered as my profit?