Let L , M , N {\displaystyle {}L,M,N} be sets, let F : L → M {\displaystyle {}F\colon L\rightarrow M} and G : M → N {\displaystyle {}G\colon M\rightarrow N} denote injective mappings. Show that the composition G ∘ F {\displaystyle {}G\circ F} is also injective.