### a) Use the histogram to complete the table.
To complete the table, we need to ensure that the frequencies for each time interval are accurately represented. From the information already given, we have:
```
\begin{tabular}{|c|c|}
\hline Time ( [tex]$t$[/tex] minutes) & Frequency \\
\hline [tex]$0\hline [tex]$30\hline [tex]$40\hline [tex]$60 \leqslant t<80$[/tex] & 20 \\
\hline [tex]$80\hline
\end{tabular}
```
Since the frequencies are already provided for each interval, the table is already complete.
### b) Use the table to complete the histogram.
To complete the histogram, you need to draw bars corresponding to each time interval with heights proportional to their frequencies. Here's how the histogram should be drawn:
1. Interval [tex]$0
- Frequency: 45
- Draw a bar from 0 to 30 on the horizontal axis with a height of 45.
2. Interval [tex]$30
- Frequency: 35
- Draw a bar from 30 to 40 on the horizontal axis with a height of 35.
3. Interval [tex]$40
- Frequency: 18
- Draw a bar from 40 to 60 on the horizontal axis with a height of 18.
4. Interval [tex]$60 \leqslant t<80$[/tex]:
- Frequency: 20
- Draw a bar from 60 to 80 on the horizontal axis with a height of 20.
5. Interval [tex]$80
- Frequency: 10
- Draw a bar from 80 to 100 on the horizontal axis with a height of 10.
By following the above steps and drawing corresponding bars, you will have a complete histogram representing the time intervals and frequencies given in the table.
