Valuation of shares

Hello friends,

I need one help from you. One of my client who has a indian company(A)  wants to take over another indian company( I ). But the indian company is a 100% subsidiary of foreign company (f). 

Now he has to purchase shares from foreign company and he wants to obtain certificate of valuation of shares from CA to be submitted to merchant banker for foreign remittance. I want to know that now valuation of share will be done on what basis( DCF or NAV method). Any FEMA or RBI regulation in this regard.

Please reply  on urgent basis.