Explanation:

Ab Ltd is not an “undertaking” as the Investment therein (i.e. 15 crores) does not exceed 20% of Co’s Net worth (20%*100 crores). So u/s 180(1)(a) GM-SR is not required .

180. Restrictions on powers of Board
(1) The Board of Directors of a company shall exercise the following powers only with the consent of the company by a special resolution, namely:—
(a) to sell, lease or otherwise dispose of the whole or substantially the whole of the undertaking of the company or where the company owns more than one undertaking, of the whole or substantially the whole of any of such undertakings.
Explanation.—For the purposes of this clause,—
(i) “undertaking” shall mean an undertaking in which the investment of the company exceeds twenty per cent. of its net worth as per the audited balance sheet of the preceding financial year or an undertaking which generates twenty per cent. of the total income of the company during the previous financial year;
(ii) the expression “substantially the whole of the undertaking” in any financial year shall mean twenty per cent. or more of the value of the undertaking as per the audited balance sheet of the preceding financial year;