## Question 6(i):

**Forward Pass / Completion Time**
$$\text{Minimum project completion time} = 10 \text{ days}$$ | M1 (at least one merge correct), A1 (answer 10) | At least one merge correct

**Backward Pass / Critical Activities**
$$\text{Critical activities: A, B, E, G, H, J, K}$$ | M1 (at least one burst correct), A1 | A, B, E, G, H, J, K

**Activity Network**
| | | | | |
|---|---|---|---|---|
| Activity | C | D | F | I |
| Float (days) | 1 | 0.5 | 1 | 0.5 |

| M1 (any one float correct), A1 (all correct), [7] | Ignore any extras

**Reference tables (ES/LF values):**

| | A | B | C | D | E |
|---|---|---|---|---|---|
| ES | 0 | 2 | 2 | 2 | 3 |
| LF | 2 | 3 | 4 | 3 | 5 |

| | F | G | H | I | J | K |
|---|---|---|---|---|---|---|
| ES | 3 | 5 | 6 | 6 | 7 | 9 |
| LF | 5 | 6 | 7 | 7 | 9 | 10 |

**Activity Network attempted** | B1 | Activity network attempted [3.3]

---

## Question 6(ii):

e.g. Activities may not start on time because of delays. May need to wait for specialist equipment or other people. | B1, B1, [2] | May give specific examples. Delays or activities overrunning. May want to avoid splitting an activity overnight when other people are involved. Any issue relating to activity start/finish times/durations. Any resourcing issue (including availability of Sheona and Tim)

---

## Question 6(iii):

Activity E cannot start until Sheona has completed A, B and D. These take $2+1+0.5 = 3.5$ days, so E cannot start until 3.5 days have elapsed. | E1 | E.g. identifying that B and D cannot be done at the same time.

But E is a critical activity, (so delaying E will delay the entire project). | E1, [2] | A delay in a critical activity will delay the whole project. This affects critical activity E (or G)

---

## Question 6(iv)(a):

Each is occupied for a total of 8 days, so the longest rest either can have is 6 days | M1 (14 - 6 or (either) busy for 8), A1 (answer 6), [2] | S does ABDEGI rests for 6 days and then does K. T does ACF rests for 6 days and then does HJK. Allow if rest for either S or T identified as 6 days.

---

## Question 6(iv)(b):

Activity G must start at the earliest on the afternoon of day 6 and at the latest on the morning of day 10.

Sheona is busy for 6.5 days before the end of activity G (and 1.5 days after activity G) and Tim is busy for 4 days after the end of activity G (and 4 days before the start of activity G).

If activities A to I are done as early as possible and activities J, K as late as possible then Sheona and Tim are both on a break from the afternoon of day 8 to the end of day 11.

$$= 3.5 \text{ days}$$ | M1 (using timing of activity G / minimum completion time $= 10.5$ days / equivalent reasoning about early/late times), A1 (3.5), [2] | May be implied from answer 3.5. Or using minimum completion time $= 10.5$ days. Or equivalent reasoning about early/late times.

---

## Question 6(iv)(c):

$$\text{A, E, G, H, J, K} = 3.5 \text{ days}$$

| | B | C | D | F | I |
|---|---|---|---|---|---|
| | 4 | 5 | 4.5 | 5 | 4 |

| M1 (activities with float $= 3.5$ days: A, E, G, H, J, K), A1 (others correct), [2] | Accept with 1 or 2 errors in total