Solution (source code)

= Solution

A <group homomorphism> $f:G\to H$ preserves the operation: $f(ab)=f(a)f(b)$ for all $a,b\in G$. A <group isomorphism> is a bijective <group homomorphism>; its inverse also preserves the operation. The <kernel of a group homomorphism> is $\ker f=\{g\in G:f(g)=e_H\}$, a <normal subgroup> of $G$.