user: Question: What is the average week that there was a game with less than 18517 fans attending and occurred on November 21, 1954?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 26, 1954', 'at San Francisco 49ers', 'L 41-7', 32085.0]
SQL:

assistant: SELECT AVG("Week") FROM "Table" WHERE "Attendance" < 18517.0 AND "Date" = 'November 21, 1954';