Long term capital gain for the property sold in fy 2017-18

I have property in Mumbai which was bought in 1989 and would like to sell in this financial year. But because of new base year changed to 2001 how the calculation will be.

As per the old calculation it was done as under - say the cost price is 48L and CII for the FY2016-17 is 1125 with CII on FY1989 was 223

Indexed Cost of Acquisition is = 4800000X1125 / 223 = Rs. 242,15,247

Say my selling price is 6 cr. so the capital Gain is 60000000-24215247 = 35,784,753/-

On that the tax to be calculated.

But due to new base rate what would be the real Indexed Cost of Acquisition as the year from 1989 to 2001 (11yrs) of indexing is lost.

Also if the new chart (as per the ratio analysis) is made then we tend to pay 13L more as taxed if it was sold in 2016-17 to 2017-18.

Please advice if my calculation is right

Thanks

Pinakin Balsara