My father accumulated a total 717 Engineers India Share from 2019 to 2021. He later participated in buyback where 717 shares were deducted from his demat account. But out of those 717 shares only 458 shares were accepted and 259 were returned back to his demat account. Question is tax on selling those 259 shares. The COA of those 259 shares will be the actual purchase price or buyback issue price or something else?