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 | 3,601 |
2 | 2,968 |
3 | 1,884 |
4 | 1,684 |
5 | 3,333 |
| 13,470 |
The next month (after spending some money on an ad) they sold 4 times as many as they had sold in the previous 5 months. How many more burgers did they sell after running the ad?