The table below shows how a firm's total cost of producing leather boots changes as output increases.
| Output (leather boots per month) | Total cost per month (£) |
|---|---|
| 0 | 60 000 |
| 2 000 | 180 000 |
| 4 000 | 280 000 |
| 6 000 | 360 000 |
What is the average fixed cost of producing 2 000 leather boots per month?
£30
£60
£90
£120
