user: ### NOW ANSWER:
Question: What is the attendance for the game against the kansas city chiefs earlier than week 13?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 16, 1973', 'at Minnesota Vikings', 'L 24–16', 44818.0]
SQL:

assistant: SELECT AVG("Attendance") FROM "Table" WHERE "Opponent" = 'kansas city chiefs' AND "Week" < 13.0;