The beanbag factory can fire or replace the third worker as he is not working to his full potential.
Explanation:
It is given all the workers in the factory that are employed are of the same level of ability.
It must also follow that working at their full potential they will be able to do the same amount of work as they were able to do previously.
The amount of work thus done by the three has diminished since the hiring of the third man which makes it evident that it is him who is causing the diminishing returns.
So it is only logical to remove the man from the workforce as he is not working to his potential or is influencing the other workers too to work less.
