4 The table lists tasks which are involved in adding a back door to a garage. The table also lists the duration and immediate predecessor(s) for each task. Each task is undertaken by one person.
| Task | Duration (hours) | Immediate predecessor(s) |
| A | measure | 0.5 | - |
| B | manufacture frame and door | 5 | A |
| C | cut hole in wall | 2 | A |
| D | fit lintel and marble step | 1.5 | C |
| E | fit frame | 1 | B, C |
| F | fit door | 1 | E |
| G | repair plaster around door | 1 | E |
- Draw an activity on arc network for these activities.
- Mark on your diagram the early time and the late time for each event. Give the minimum completion time and the critical activities.
- Produce a schedule to show how two people can complete the project in the minimum time.
Soon after starting activity D , the marble step breaks. Getting a replacement step adds 4 hours to the duration of activity D.
- How does this delay affect the minimum completion time, the critical activities and the minimum time needed for two people to complete the project?
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