user: Question: What was the year opened for North Carolina with a smaller than 21500 capacity?
Columns: ['Rank', 'Capacity', 'City', 'State', 'Year opened']
Types: ['text', 'real', 'text', 'text', 'text']
Sample row: ['1', 109901.0, 'Ann Arbor', 'Michigan', '1927']
SQL:

assistant: SELECT "Year opened" FROM "Table" WHERE "State" = 'North Carolina' AND "Capacity" < 21500.0;