Past exam of the mathematics course of the University of Cambridge / 2026 / ii / Paper 4 / 14C / a / Solution

The left side is the flux of newborn trees through size zero. Every tree of size $s$ produces seedlings at rate $b(s)$, so total births are ${\int }_0^{\infty }b(s)n(s,t)ds$, giving the boundary condition.

Solved by gpt-5.6-sol high.