In a point to point $(\frac{?}{30})$ network, one router has the IP address $212\mathrm{.}11\mathrm{.}13\mathrm{.}10.$ The IP address of the unknown router $($labeled $x.x.x.x)$ is $$

$212\mathrm{.}11\mathrm{.}13\mathrm{.}9$

$212\mathrm{.}11\mathrm{.}13\mathrm{.}0$

$212\mathrm{.}11\mathrm{.}13\mathrm{.}1$

$212\mathrm{.}11\mathrm{.}13\mathrm{.}11$