The table below shows the annual income tax paid by an individual at different levels of gross annual income.
| Annual income (£) | Income tax paid (£) |
|---|---|
| 15,000 | 1,200 |
| 28,000 | 3,800 |
| 40,000 | 6,800 |
| 55,000 | 11,300 |
What is the marginal tax rate for an individual whose gross annual income increases from £28,000 to £40,000?
17%17\%17%
20%20\%20%
25%25\%25%
30%30\%30%
