D2 June 2013 Q7
7. Nigel has a business renting out his fleet of bicycles to tourists.
At the start of each year Nigel must decide on one of two actions:
- Keep his fleet of bicycles, incurring maintenance costs.
- Replace his fleet of bicycles.
The cost of keeping the fleet of bicycles,
the cost of replacing the fleet of bicycles
and the annual income are dependent on the age of the fleet of bicycles.
Table 1 shows these amounts, in £1000s.
| Age of fleet of bicycles | new | 1 year old | 2 years old | 3 years old | 4 years old |
|---|---|---|---|---|---|
| Cost of keeping (£1000s) | 0 | 1 | 2 | 3 | 8 |
| Cost of replacing (£1000s) | – | 7 | 8 | 9 | 10 |
| Income (£1000s) | 11 | 8 | 5 | 2 | 0 |
Table 1
Nigel has a new fleet of bicycles now and wishes to maximise his total profit over the next four years.
He is planning to sell his business at the end of the fourth year.
The amount Nigel will receive will depend on the age of his fleet of bicycles.
These amounts, in £1000s, are shown in Table 2.
| Age of fleet of bicycles at end of 4th year | 1 year old | 2 years old | 3 years old | 4 years old |
|---|---|---|---|---|
| Amount received at end of 4th year (£1000s) | 6 | 4 | 2 | 1 |
Table 2
Complete the table in the answer book to determine Nigel’s best strategy to maximise his total profit over the next four years. You must state the action he should take each year (keep or replace) and his total profit. (13)
| Scheme | Marks | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1M1 A1 A1 2M1 A1 3M1 A1ft A1 4M1 A1ft A1 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| The actions Nigel should take are: Keep, Keep, Replace, Keep in years 1, 2, 3 and 4 respectively His income will be £32 000. | B1 B1ft | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| (13 marks) |
Notes
1M1 At least 3 columns in Stage 4 completed, something in each cell.
1A1 For stage 4 at least two columns of state, action, destination entries correct
2A1 Two rows in Stage 4 CAO. Penalise * errors only twice in the question on the first occurrences
All future M marks must bring all optimal results from previous stage into current stage at least once (or three out of four previous results correct).
2M1 All four rows in stage 4 completed. Bod if something in each cell.
3A1 CAO. Stage 4 correct. (Penalise * errors only twice in the question).
3M1 Stage 3 completed. Bod if something in each cell.
4A1ft Any state correct (Penalise * errors only twice in the question).
5A1 CAO Both states correct. (Penalise * errors only twice in the question).
4M1 Stage 2 and 1 completed. Bod if something in each cell.
6A1ft CAO Stage 2 correct. (Penalise * errors only twice in the question).
7A1 CAO Stage 1 correct.
1B1 Actions correct. Must have earned all previous M marks
2B1ft Income correct for their table. Must have earned all previous M marks.
Penalise extra rows for stage 4 with the 3rd A mark, stage 3 with the 5th A mark and stage 2 with the 6th A mark.