P/E ratio changes vs P/E ratio remains constant after the acquisition

https://opentuition.com/topic/louieed/
1) So if the P/E was to change post acquisition, then we would use the combined company valuation technique?

“1. You would apply the new PE to the new earnings.”

I found this answer from a previous post.

Sir, I have a doubt in regards to calculation of the P/E ratio.
In most of the questions related to Mergers and Acquisition, the examiner specifically says that the “PE ratio remains constant after the acquisition”.
So then we use the P/E ratio of Predator Company to calculate the total value of the combined company.

Sir lets say if the P/E ratio changes after the acquisition, then to calculate the value of the combined entity we apply NEW P/E to the new earnings right?

But how do we calculate this NEW P/E ratio. Is it calculated as,
NEW P/E = (MPS of Predator Co + MPS of Target Co)/ New EPS based on new earnings

or
Is there are any other methods to calculate this NEW P/E ratio?

Thanking you in advance for your kind explanation!