A new fast food restaurant opened 5 months ago. The table belows shows the number of burgers they've sold so far.
Month | Burgers Sold |
1 | 2,245 |
2 | 3,856 |
3 | 2,028 |
4 | 3,395 |
5 | 3,944 |
| 15,468 |
The next month (after spending some money on an ad) they sold 7 times as many as they had sold in the previous 5 months. How many more burgers did they sell after running the ad?