Hi Sarah,
I think if the user input an orgid that doesn't exist in the table orgunits, then you should raise exception invalid orgid.
Ex.
select * from q3(20000, 35,100);
Because there's no organization with the id 20000, the exception invalid orgid is raised
I'm not a tutor, but that's how I did in my solution... you might want to confirm with one of the tutors
Best,
Paula