The following table shows the total number of votes polled and the percentage of invalid votes in a polling center in a village during the last four Assembly elections.
| Year | Total votes polled | Percentage of Invalid votes |
| 2005 | 6500 | 5% |
| 2010 | 8000 | 7% |
| 2015 | 9400 | 15% |
| 2020 | 10400 | 12% |
What is the sum of the number of valid votes polled in 2010 and 2015 at this center?