In: Advanced Math
3. Let F : X → Y and G: Y → Z be functions.
i. If G ◦ F is injective, then F is injective.
ii. If G ◦ F is surjective, then G is surjective.
iii. If G ◦ F is constant, then F is constant or G is constant.
iv. If F is constant or G is constant, then G ◦ F is constant.