In my CRM module, I configured several property fields (like estimated cost, objective price etc).

Howeever, when I try to used these fields, I cant find the way to use them. 

I already read the properties documentation from odoo

In the example below, all of the fields and properties. All of them are decimals.

I need the Costo Total (Total Cost) field to be the sum of all the other fields, but I cant find the technical name of the fields, in order to add them with a python code.

What could I do?