user: Question: What is the average Attendance, when Venue is "Candlestick Park", and when Date is "December 27"?
Columns: ['Year', 'Date', 'Home Team', 'Result', 'Visiting Team', 'Venue', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'real']
Sample row: [1990.0, 'November 25', 'San Francisco 49ers', '17-28', 'Los Angeles Rams', 'Candlestick Park', 62633.0]
SQL:

assistant: SELECT AVG("Attendance") FROM "Table" WHERE "Venue" = 'Candlestick Park' AND "Date" = 'December 27';