SELECT year_opened FROM track WHERE seating BETWEEN 4000 AND 5000
What are the years of opening for tracks with seating between 4000 and 5000?
[Schema (values) (types)]: | race_track |  race : race_id (text) , name (number) , class (text) , date (text) , track_id (text) | track : track_id (text) , name (number) , location (text) , seating (text) , year_opened (text);