What BEST can be said about object o8?
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Correct answer: C
The valuation table (how much each person values each object):
| Person | o1 | o2 | o3 | o4 | o5 | o6 | o7 | o8 | o9 | o10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Amar | 4 | 9 | 9 | 3 | 7 | 3 | 8 | 7 | 9 | 5 |
| Barat | 5 | 9 | 7 | 5 | 5 | 3 | 6 | 8 | 10 | 8 |
| Charles | 8 | 8 | 8 | 3 | 6 | 4 | 5 | 8 | 9 | 6 |
| Disha | 8 | 8 | 8 | 5 | 5 | 3 | 6 | 4 | 9 | 8 |
| Elise | 6 | 8 | 9 | 5 | 6 | 5 | 6 | 3 | 7 | 10 |
Each person receives a bundle of exactly two objects; a bundle's worth to a person is the sum of that person's two values.
Working out the whole distribution (once).
- The two 10's are forced. If someone values an object at 10, they must get it. The only 10's are Barat → o9 and Elise → o10. So Barat gets o9, Elise gets o10.
- Barat is pinned to a total of 16. Barat already holds o9 (worth 10 to him). His total must be even and at most 16, so his second object must be worth an even number no more than 6 to him. The only such value in his row is o7 = 6. So Barat = {o9, o7} = 16.
- Elise also totals 16. She holds o10 (worth 10). Her second object must be even and at most 6 to her: the choices are o1, o5, o7 (each 6). o7 is taken, so Elise = {o10, o1} or {o10, o5}, worth 16.
- The third 16 is Charles, not Amar. Amar would value Barat's bundle {o9, o7} at 9 + 8 = 17. If Amar's own bundle were also 16, he would envy Barat — but a person on the top value of 16 is not allowed to envy anyone. So Amar is below 16, and the third person at 16 is Charles, who reaches 16 only with two objects each worth 8 to him — two of {o1, o2, o3, o8}.
- Charles must hold o8. Objects o1, o2, o3 go to three different people, so Charles can't take two of those; and o1 and o8 go to different people, so {o1, o8} is out. The only pairs left are {o2, o8} and {o3, o8} — both contain o8, so o8 → Charles.
- Charles = {o3, o8}. If Charles held {o2, o8}, Barat would value it at 9 + 8 = 17 and would envy him — not allowed. So Charles = {o3, o8} = 16, leaving o2 free.
- Elise = {o10, o5}. The other choice, {o10, o1}, leaves no way to finish without breaking a rule, so Elise = {o10, o5} = 16.
- The last four objects {o1, o2, o4, o6} split between Amar and Disha. Disha's total must be odd, Amar's even. The only split that works is Amar = {o2, o6} = 9 + 3 = 12 and Disha = {o1, o4} = 8 + 5 = 13.
The complete result:
| Person | Bundle | Own value |
|---|---|---|
| Amar | o2, o6 | 12 |
| Barat | o9, o7 | 16 |
| Charles | o3, o8 | 16 |
| Disha | o1, o4 | 13 |
| Elise | o10, o5 | 16 |
This question — object o8. Steps 5 and 6 show that every possible 16-bundle for Charles contains o8, and the distribution places it with him.
Answer: o8 was given to Charles
