The frequencies of the number of letters consisting of 50 names and 50 surnames taken from a telephone directory are given in the table. Find the difference between the number of names with less than 13 letters and the number of surnames with less than 10 letters.
| Number of Letters | Number of names | Number of surnames |
| 1-4 | 5 | 0 |
| 4-7 | 16 | 9 |
| 7-10 | 18 | 19 |
| 10-13 | 8 | 18 |
| 13-17 | 3 | 4 |
1
1
2
4
3
3
4
19