The table below shows information about the time, in minutes, that 40 people spent exercising at a gym yesterday.
| Time (t t\,t minutes) | Number of People |
|---|---|
| 0 to 4 | 5 |
| 5 to 9 | 12 |
| 10 to 14 | 10 |
| 15 to 19 | 8 |
| 20 to 24 | 5 |
Calculate an estimate for the mean time spent exercising.