Answer:
I will answer this in English, we can translate it to:
Why if you charge a mate by an amount of time you are not doing work?
This happens because work is defined as the displacement done by a force:
W = d*F
where W is work, d is the distance, and F is the force.
This means that the amount of time that you are charging your mate does not affect the mechanical work, the only time that you are doing work is when you are lifting him.
