The table below shows the annual income and the total income tax paid by an individual at different income levels.
| Annual Income | Tax Paid |
|---|---|
| £30 000 | £3 000 |
| £40 000 | £6 000 |
| £50 000 | £10 000 |
| £60 000 | £15 000 |
| £70 000 | £21 000 |
What is the change in the average tax rate for an individual if their annual income increases from £40 000 to £50 000?
4%
5%
8%
10%
