4 A communications company is conducting a feasibility study into the installation of underground television cables between 5 neighbouring districts.
The length of the possible pathways for the television cables between each pair of districts, in miles, is shown in the table.
The pathways all run alongside cycle tracks.
| Billinge | Garswood | Haydock | Orrell | Up Holland |
| Billinge | - | 2.5 | *** | 4.3 | 4.8 |
| Garswood | 2.5 | - | 3.1 | *** | 5.9 |
| Haydock | *** | 3.1 | - | 6.7 | 7.8 |
| Orrell | 4.3 | *** | 6.7 | - | 2.1 |
| Up Holland | 4.8 | 5.9 | 7.8 | 2.1 | - |
4
- Give a possible reason, in context, why some of the table entries are labelled as ***.
4
- As part of the feasibility study, Sally, an engineer needs to assess each possible pathway between the districts. To do this, Sally decides to travel along every pathway using a bicycle, starting and finishing in the same district. From past experience, Sally knows that she can travel at an average speed of 12 miles per hour on a bicycle.
Find the minimum time, in minutes, that it will take Sally to cycle along every pathway.
[0pt]
[4 marks]