6 The table shows the tasks involved in making a batch of buns, the time in minutes required for each task, and their precedences.
| Task | Time (minutes) | Immediate predecessors |
| A | measure out flour | 0.5 | - |
| B | mix flour and water | 1 | A |
| C | shell eggs | 0.5 | - |
| D | mix in eggs and fat | 2 | B, C |
| E | get currants ready | 0.5 | - |
| F | get raisins ready | 0.5 | - |
| G | fold fruit into mix | 0.5 | D, E, F |
| H | bake | 10 | G |
- 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.
Preparing the batch for baking consists of tasks A to G ; each of these tasks can only be done by one person. Baking, task H, requires no people.
- How many people are required to prepare the batch for baking in the minimum time?
- What is the minimum time required to prepare the batch for baking if only one person is available?
Jim is preparing and baking three batches of buns. He has one oven available for baking. For the rest of the question you should consider 'preparing the batch for baking' as one activity.
- Assuming that the oven can bake only one batch at a time, draw an activity on arc diagram for this situation and give the minimum time in which the three batches of buns can be prepared and baked.
- Assuming that the oven is big enough to bake all three batches of buns at the same time, give the minimum time in which the three batches of buns can be prepared and baked.