Solution

ID: past-exam-of-the-probability-statistics-and-options-ii-course-of-the-university-of-oxford/2008/r/2/v/solution

As established above, . Select any three vertices in each parity class; all nine edges between the two triples are present, giving a subgraph. A planar graph has only planar subgraphs, whereas is nonplanar by the permitted result. Therefore .

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