 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/ib/paper-1/19h/b/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

The graph has six edges, and

A

has degree one. Hence

π_{A} = 1/12

. Kac's return-time formula gives

E_{A} T_{A}^{+} = \frac{1}{π _{A}} = 12.

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