Past exam of the mathematics course of the University of Cambridge 2023 ib Paper 4 7H c Solution Created 2026-09-24 Updated 2026-10-03
Let be the expected number of visits to state before absorption, counting the present state when . Its reward equations areThe last equation gives , so the second nontrivial equation gives . Hence , andThus the expected occupation count is two; together with the previous parts, this is the four-state reflecting absorbing random walk calculation.