Sending Notifications

In Asana, I have a project with two approvers in different sections. If the last approver disapproves the request, I want an email notification to be sent to both the form submitter and the second approver (the department head). Although I can set a rule to send an email notification to the form submitter, how can I also ensure that the department head (the second approver) receives the same notification when the request is disapproved?

Are they both collaborators on the task?