Extensions spec.json

[Cognos91]

Hi,
We are using silent install for installing Cognos 11.2.4 fp3.
I need to be able to hide the welcome banner, quick launch and get started sections on the welcome page. I will be retaining the Recent tab.
I have a spec.json file that works. So, I tested this manually via uploading the zip file manually to the Extensions tab in the UI. This works.

Now my question is: where does this zip file land in the cognos install directory? Does it land in the extensions folder or the webcontent > bi folder?

I need to automate the upload of extensions into Cognos UI, so just need some insights on the same.