The table below gives the number of United States presidents from 1789 to 2015 whose age at the time they first took office is within the interval listed.
| Ages | Number |
|---|---|
| 40-44 | 2 |
| 45-49 | 7 |
| 50-54 | 13 |
| 55-59 | 11 |
| 60-64 | 7 |
| 65-69 | 3 |
What fraction of all presidents listed in the table were between 50 and 59 years old, inclusive, when they first took office?
