How to calculate Feeding Buffer?

I found this that explain in simple term
The difference between project buffer vs feeding buffer vs resource buffer
http://innovativeprojectguide.com/project-...rce-buffer.html

Project Buffer
It is a reserve inserted at end of the project. Any delay in the Longest Path will consume some or all of the buffer, and the completion date will not change.

Feeding Buffers:
It is a buffer that is inserted before the first activity on the Critical Chain. This is to ensure that any tasks feeding into the Critical Chain may not delay the Critical Chain. When a delay does occur in the feeding activities, the feeding buffer is consumed so that Critical Chain is not affected.

Resource Buffers:
These are dummy activities with critical resource assignment, added at one or more places on the Critical Chain with so as to ensure that the resource is available and committed to be utilized if needed.