D1 January 2009 Q3
3.
(a) Draw the activity network described in this precedence table, using activity on arc and exactly two dummies. (5)
| Activity | Immediately preceding activities |
|---|---|
| A | - |
| B | - |
| C | - |
| D | B |
| E | B, C |
| F | B, C |
| G | F |
| H | F |
| I | G, H |
| J | I |
(b) Explain why each of the two dummies is necessary. (2)
| Scheme | Marks |
|---|---|
 | M1 A1 A1 A1 A1 |
| (5) |
Notes
(a) 1M1: one start and A to C and one of D, E or F drawn correctly
1A1: 1st dummy (+arrow) and D, E and F drawn correctly
2A1: G, H, I and J drawn in correct place
3A1: second dummy (+arrow) drawn in a correct place
4A1: cso. all arrows and one finish.
| Scheme | Marks |
|---|---|
| 1st dummy – D depends on B only, but E and F depend on B and C | B1 |
| 2nd dummy – G and H both must be able to be described uniquely in terms of the events at each end. | B1 |
| (2) | |
| (7 marks) |
Notes
(b) 1B1: cao, but B, C, D, E and/or F referred to, generous
2B1: cao, but generous.