Past exam of the mathematics course of the University of Cambridge 2021 iii Paper 204 2 c Solution 2026-09-28
The events decrease, and an open path from reaches every exactly when the open cluster of is infinite. Therefore continuity from above of a measure givesEach depends on finitely many sites, so is a polynomial and hence continuous. Given , choose with . For , monotonicity and the finite-event continuity yieldThus from the right.