6 The table shows the tasks involved in making a salad, their durations and their precedences.
| Task | Duration (seconds) | Immediate predecessors |
| B | get out bowl and implements | 10 | - |
| I | get out ingredients | 10 | - |
| L | chop lettuce | 15 | B, I |
| W | wash tomatoes and celery | 25 | B, I |
| T | chop tomatoes | 15 | W |
| C | chop celery | 10 | W |
| P | peel apple | 20 | B, I |
| A | chop apple | 10 | P |
| D | dress salad | 10 | L, T, C, A |
- Draw an activity on arc network for these activities.
- Mark on your diagram the early and late times for each event. Give the minimum completion time and the critical activities.
- Given that each task can only be done by one person, how many people are needed to prepare the salad in the minimum time?
What is the minimum time required to prepare the salad if only one person is available?
- Show how two people can prepare the salad as quickly as possible.