user: Question: When was construction completed that was listed on 09/21/1984 and a Deleted of 11/04/1999?
Columns: ['CERCLIS ID', 'Name', 'County', 'Proposed', 'Listed', 'Construction completed', 'Partially deleted', 'Deleted']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['IDD000800961', 'Arrcom (Drexler Enterprises)', 'Kootenai', '12/30/1982', '09/08/1983', '06/30/1992', '–', '12/23/1992']
SQL:

assistant: SELECT "Construction completed" FROM "Table" WHERE "Listed" = '09/21/1984' AND "Deleted" = '11/04/1999';