$2.$ Subnetwork S$,$ to which a computer with an IP of $155\mathrm{.}212\mathrm{.}24\mathrm{.}31$ belongs, can accommodate $128(=27)$ nodes. Let's name the four smaller networks that divide this subnetwork into four equal parts, $\backslash (\backslash$mathrm$\{$SO$\},\backslash$mathrm$\{$S$\}1,\backslash$mathrm$\{$~S$\}2\backslash ),$ and S $3,$ in order of the numerical size of the network addresses $($the network with the smallest number of network addresses is SO$).$ Then, write down the network address of the following mixed network.

$(1)$ Mixed network of SO and S$1($multiple networks combined into one$)$

$(2)$ Mixed network of S$1$ and S$2$

$(3)$ Mixed network of S$2$ and S$3$