D1 June 2019 Q5
5.
| Activity | Immediately preceding activities |
|---|---|
| A | – |
| B | – |
| C | A |
| D | A |
| E | A, B |
| F | C, D |
| G | D |
| H | D, E |
| I | F, G |
| J | F, G, H |
It is given that activity C is a critical activity.
| Scheme | Marks |
|---|---|
 | M1 A1 A1 A1 A1 |
| (5) |
Notes
In (a) condone lack of, or incorrect, numbered events throughout. ‘Dealt with correctly’ means that the activity starts from the correct event but need not necessarily finishes at the correct event, e.g. ‘F dealt with correctly’ requires the correct precedences for this activity, i.e. C and D labelled correctly and leading into the same node and F starting from that node but do not consider the end node for F. Activity on node is M0
If an arc is not labelled, for example, if the arc for activity G is not labelled (but the arc is present) then this will lose the second A mark and the final (CSO) A mark – they can still earn the third A mark on the bod. If two or more arcs are not labelled then mark according to the scheme. Assume that a solid line is an activity which has not been labelled rather than a dummy (even if in the corrct place for where a dummy should be)
Ignore incorrect or lack of arrows on the activities for the first four marks only
a1M1: Eight activities (labelled on arc), one start and at least two dummies placed
a1A1: Activities A, B, 1st dummy (+ arrow) and C, D and E dealt with correctly
a2A1: 2nd and 3rd dummies (+ arrow) and F, G and H dealt with correctly
a3A1: Activities I, J and 4th dummy (+ arrow) dealt with correctly
a4A1: CSO – all arrows present and correctly placed with one finish – please check all arcs carefully for arrows
Note that additional (but unnecessary) ‘correct’ dummies that still maintain precedence for the network should only be penalised with the final A mark if earned
| Scheme | Marks |
|---|---|
| In the network there must be at least one critical path from the start node to the end node and as all paths must pass through either I or J (as these are the only two activities that go into the end node) so one of these must be critical | B1 |
| (1) |
Notes
b1B1: CAO (must either mention that any critical path for the network would need to pass through either I or J
| Scheme | Marks |
|---|---|
| A and F must be critical | B1 |
| (1) | |
| 7 marks |
Notes
c1B1: CAO (with no additional activities – so accept A, F or A, C, F only but not A, (C), F, I or J)