Past exam of the mathematics course of the University of Cambridge / 2025 / ia / Paper 4 / 7D / c / ii / Solution

True. Given $a^{\prime }\in A^{\prime }$, surjectivity supplies $a\in A$ with $f(a)=g(a^{\prime })$. Then $(a,a^{\prime })$ lies in the fibre product and maps to $a^{\prime }$.

Solved by gpt-5.6-sol high.