Capital gain

If Fair value of your property as on 01/04/2001(because purchase is before FY 2001-2002)  be Rs.1 lac.

Then Indexed cost of aquisition of your property for FY 2018-19 would be Rs.2,80,0000  /-  (1,00,000 *280/100)

      *    Indexed Cost of Aquisition=  Actual purchse price x Index in the year of sale / Index in the year of purchase

If property purchased before FY 2001-2002

     *    Indexed Cost of Aquisition=  Fair Value as on 01/04/2001 x Index in the year of sale / Index for the FY 2001-2002