user: Question: When is the earliest year opened for huff hall that was established after 1974?
Columns: ['Team', 'Established', 'Big Ten Conference Titles', 'National Titles', 'Venue', 'Opened', 'Capacity']
Types: ['text', 'real', 'real', 'real', 'text', 'real', 'real']
Sample row: ['Illinois Fighting Illini football', 1890.0, 15.0, 5.0, 'Memorial Stadium', 1923.0, 60670.0]
SQL:

assistant: SELECT MIN("Opened") FROM "Table" WHERE "Venue" = 'huff hall' AND "Established" > 1974.0;