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For each function given below, determine whether or not the function is injective and whether or not the function is surjective.

1. \(f:\N \to \N\) given by \(f(n) = n+4\text{.}\)

2. \(f:\Z \to \Z\) given by \(f(n) = n+4\text{.}\)

3. \(f:\Z \to \Z\) given by \(f(n) = 5n - 8\text{.}\)

4. \(f:\Z \to \Z\) given by \(f(n) = \begin{cases}n/2 \amp \text{ if } n \text{ is even} \\ (n+1)/2 \amp \text{ if } n \text{ is odd} . \end{cases}\)