7 A random sample of 97 people who own mobile phones was used to collect data on the amount of time they spent per day on their phones. The results are displayed in the table below.
| Time spent per | | day \(( t\) minutes \()\) |
| \(0 \leqslant t < 5\) | \(5 \leqslant t < 10\) | \(10 \leqslant t < 20\) | \(20 \leqslant t < 30\) | \(30 \leqslant t < 40\) | \(40 \leqslant t < 70\) |
| 11 | 20 | 32 | 18 | 10 | 6 |
- Calculate estimates of the mean and standard deviation of the time spent per day on these mobile phones.
- On graph paper, draw a fully labelled histogram to represent the data.