D1 January 2012 Q1
1.

Figure 1 represents the distances, in km, between eight vertices, A, B, C, D, E, F, G and H in a network.
| Scheme | Marks |
|---|---|
| DC, EG, CF, reject DF; AD, BC, reject AB, BE, reject EF and FG, DH | M1; A1 A1 |
| (3) |
Notes
a1M1: First three arcs correctly chosen and DF rejected. Accept weights for all 3 marks.
Special case: If all 7 arcs, in correct order, but no rejections seen at all, then award M1 only.
a1A1: All arcs/weights in tree selected correctly at correct time.
a2A1: All rejections correct and at the right time.
| Scheme | Marks |
|---|---|
| AD, DC, CF, CB; BE; EG, DH | M1;A1; A1 |
| (3) |
Notes
b1M1: First four arcs/weights correctly chosen, or first five nodes ADCFB chosen in order.
Special case : If Prim but not starting at A please send to review.
b1A1: First five arcs/weights correctly chosen, or all nodes in order A, D, C, F, B, E, G, H.
b2A1: CSO (must be arcs/weights). E.g no ‘reject’ arcs
| Scheme | Marks |
|---|---|
![]() | B1 |
| (1) |
Notes
c1B1: CAO mark what you see at (c).
| Scheme | Marks |
|---|---|
| Weight of tree = 148 (km) | B1 |
| (1) | |
| (8 marks) |
Notes
d1B1: CAO mark what you see at (d).
