Answer:
Staff authority.
Step-by-step explanation:
In this case, Joan is exhibiting the type of staff authority.
This type of authority occurs when consulting with other line managers, providing them with ideas and advice, as seen in the question in the excerpt that says, "Sometimes Joan makes strong suggestions about how other managers should deal with problems of your employees ".
Therefore, despite providing advice, it is necessary that the suggestions and ideas are approved by the superiors of each manager so that it can be implemented.