Explanation:

- Initially, 8 men make 12 chairs in 12 days, working 6 hours a day.

- This means: total hours = 8 men * 12 days * 6 hours = 576 man-hours for 12 chairs.

- Therefore, per chair: 576 man-hours / 12 chairs = 48 man-hours per chair.

- Now, to make 9 chairs: 9 chairs * 48 man-hours = 432 man-hours required.

- We have 12 men and 6 days: total available hours = 12 men * 6 days = 72 man-days.

- So, 432 man-hours / 72 man-days = 6 hours per day.

- Correct Option: 6 hours (Option 2).