What is the result of the following SQL query?

SELECT employee$\_$id FROM employees

INTERSECT

SELECT employee$\_$id FROM former$\_$employees;

Retrieves employee IDs from

'former$\_$employees' table that do not exist in 'employees' table.

Retrieves all employee IDs from the 'employees' table.

Retrieves employee IDs from 'employees' table that do not exist in 'former$\_$employees' table.

Retrieves employee IDs that exist in both 'employees' and 'former$\_$employees' tables.