Price discovery in demerger?

So Aarti Industries is going to demerge its pharma business and 20th October is record date. Today the share price is quoting around Rs 702. And closing price last two days is…

Oct 18, 2022 → Rs 744

Oct 17, 2022 → Rs 788

The demerged entity will be listed in mid-december.

Wanted to understand how is the price of stock (parent and demerged companies) determined.

The pre-demerger company valued is at Rs 788 / share (17th oct). Now only chemicals business is valued at Rs 702 / share (ex record date). How has market came to this price? Will the new pharma business will be valued around Rs 88 per share? If not then at what price will be the pharma business listed?