Number of Modbus Master licenses required in one project

Hello everyone

I have 315 2PN/DP and I want to connect 10 

Now the question is the following, is it okay to do so? (10 communication processors for 1 CPU?)

and regarding the following license :

SIMATIC S7, MODBUS MASTER V3.1 SINGLE LICENSE 6ES7870-1AA01-0YA1

How many should I buy for this one project, 10? or 1 ? does every card require a license ? or the license is for the whole project as long as it is 1 plc?

does the license come with some kind of a hardware part that I have to install in the back rack?

Thank you

This will answer your question:

https://support.industry.siemens.com/cs/ww/en/view/13211560 (but this post is really old...)

But the question is, if you really need 10 masters, because one 1 master could have multiple slaves.

Look at this Application:

https://support.industry.siemens.com/cs/de/en/view/109474714