Sarah recorded the time, t t\,t minutes, that 40 students spent on their homework one evening. The table shows information about her results.
| Time (t t\,t minutes) | Frequency |
|---|---|
| 0<t≤200 < t \leq 200<t≤20 | 8 |
| 20<t≤3020 < t \leq 3020<t≤30 | 12 |
| 30<t≤4030 < t \leq 4030<t≤40 | 11 |
| 40<t≤5040 < t \leq 5040<t≤50 | 6 |
| 50<t≤7050 < t \leq 7050<t≤70 | 3 |
Calculate an estimate for the mean time spent on homework.
