Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What was the attendance on 31 January 2009 when the opponent was Airdrie United?

### Inputs:
table_name: table, columns: ['Date', 'Opponent', 'Venue', 'Result', 'Attendance']

### Response:
SELECT AVG Attendance FROM table WHERE Opponent = airdrie united AND Date = 31 january 2009