Pagdi Property Capital Gain Calculation

My Father bought Property in the year 2004 -Pagdi System-Chq Payment Zero
The landlord Vacated us without any money and broke the building in 2011
In 2013 agreed for Alternate accommodation with  Builder
In 2015 Agreement for New House made-To develop new house in 3 years with monthly rent
In 2021 Agreement Cancelled and Landlord has paid lump sum amount.
Can you please help me to calculate Capital Gain?