A large number of consecutive IP address are available starting at $198\mathrm{.}16\mathrm{.}0\mathrm{.}0.$ Suppose that four organizations, $A,B,C,$ and $D,$ request $4000,2000,4000,$ and $8000$ addresses, respectively, and in that order. For each of these, give the first IP address assigned, the last IP address assigned, and the mask in the w$.$x$.$y$.$z$/$s notation. $(10$p$)$

Why does UDP exist?