user: Question: What is the average enrollment of the Redbirds' school?
Columns: ['Institution', 'Location', 'Founded', 'Affiliation', 'Enrollment', 'Nickname']
Types: ['text', 'text', 'real', 'text', 'real', 'text']
Sample row: ['University of Illinois', 'Urbana, IL', 1867.0, 'Public', 42606.0, 'Fighting Illini']
SQL:

assistant: SELECT AVG("Enrollment") FROM "Table" WHERE "Nickname" = 'Redbirds';