Lal Ltd., a domestic company, purchases its own unlisted shares on 17th August 2021. The consideration for buyback amounted to Rs. 18 lakh, which was paid on the same day. Lal Ltd. had received Rs. 11 lakh on the issue of these shares one year back. Compute the additional income-tax payable by Lal Ltd. Further, determine the interest, if any, payable if such tax is paid to the credit of the Central Government on 7th November 2021. Discuss.