Creating a "Monthly Billing" table

Hello guys!
I would like help creating a “Monthly Billing” table.

The question is: I have a table called “Jobs” where I add all the jobs that my clients ask me for, this table contains several columns, including a “month/year”, and also a column referring to the value of each job requested. Now I would like to create a table referring to the “Monthly Billing”, containing the “Gross Monthly Billing” and the “Net Monthly Billing”.

In “Monthly Gross Billing” I would like it to be the sum of the value of all jobs referring to month “X” in the “Jobs” table and in “Monthly Net Billing” I would like it to be {Monthly Gross Billing} - all values ​​from column “Cost/Month” of a third table called “Cost of Operation”.

It would be very important that this table called “Monthly Billing” could be organized by Month.

I’m new to Airtable so I’m still learning how it works, thanks so much for all the help.

I put some pictures of my tables to make it easier to understand.