Setting up diffrent menus for diffrent visitors with subdomains

Hello!

I am helping a client with a “Learning center” for their application with 3 different manuals.

The customer want two different start pages:

A.learningcenter.com

And

B.learningcenter.com

—

A.learningcenter.com should contain 3 of total 3 manuals for their application.

B.learnincenter.com should contain 1 of 3 manuals for their application.

All administrations for the Learning Center should be done in one administration panel.

Do you have any suggestion of how to set this up?

Kind regards