Calculating value of company

Dear John,

When provided with the following details, which is the correct method of calculating post aquisition company value? :

Details
-Most recent profit after tax for aquirer and aquirer on their own, pre aquisition
-P/E ratio after aquisition
-Synergy p.a. created from aquisition

I am uncertain if I should use bootstrapping or add synergy onto individual company values pre aquisition

My uncertainty arises because the P/E ratio of joint company post aquisition is LESS than the P/E ratio of the acquiree company on its own. Does it have a bearing on which method I should use the fact that it is less?

Kind regards