demerger accounting

how to do demerged gain entries in the books?

facts:

A ltd. has 49% in B ltd BLtd. demerged in two parts C ltd and other bussiness C ltd issued Shares to share holders of B ltd  in consideration of Assets transfered by B Ltd to C ltd . Then D ltd aquired All business of C ltd and issued shares of D to share holder of C ltd.

how to calculate Capital Gain in the books of Altd who holds 49 % shares in B ltd?

how to do accounting entries in case of demerger?