3. [3 marks] Determine whether each of the following functions from Z to Z is one-to-one. If it is not, then justify. \begin{array}{l} \text { (a) } f(n)=n-10 \\ \text

{ (b) } f(n)=n^{2}+3 \\ \text { (c) } f(n)=16\left[\frac{n}{7}\right\rfloor \end{array}