$1.$ ISP #$1$ provides exclusive Internet connectivity to ISP #$2$ with customers A$,$ B$,$ C and D$.$ a$)(4$ points$)$ Suppose ISP #$2$ is given the range $195\mathrm{.}128\mathrm{.}0\mathrm{.}0$ to $195\mathrm{.}128\mathrm{.}255\mathrm{.}255.$ ISP #$2$ turns around and allocates the entire range to its four customers A$,$ B$,$ C$,$ D$.$ List the four allocations ISP #$2$ makes to A$,$ B$,$ C and D in the prex$/$mask notation.