Can you help me describing me wich type of merger is Pfizer$/$Segean $2023,13$ december was?

If its a horizontal$/$vertical$...$ Benefit to shareholders, share price reaction...

And also $\text{'}\text{'}$You should provide a short review of the academic literature in the field, focusing on the wealth impact of merger activity.? $\text{'}\text{'}$

Can you answer this.