Answer:
Better-educated people make their coworkers more productive.
Step-by-step explanation:
An external benefit or positive externality is a term that describes the benefit of an activity, that is given to a party that is not part of the actual activity. Hence, external benefit of education is the educational benefit given to a party, that is not actual part of the educational activity or process, such as making people around the educated individual to be productive or informative.
Hence, in this case, the external benefit of education is "Better -Educated people make their coworkers more productive", as those coworkers and the company at large, are benefiting from the educated individual.