$8)$ Two stations $($A$)$ and $($B$)$ on a communication line use the

Selective$-$Reject ARQ protocol, $100-$Mbps cards and a $1000-$bit

frame. The distance between the two stations is $100$ km and the

velocity is $2\backslash$times $108$ m$/$s$.$ Assume a full duplex line and a window size of

$100.$

The BER to achieve an efficiency of $50\%$ is approximately:

$($a$)5$x$10-4($b$)5$x$10-6($c$)5$x$10-3($d$)$ neither a$,$ b or c

$($a$)($b$)($c$)($d$)$

The solution for improving the communications between stations A

and B is:

$($a$)$ decrease BER $($b$)$ decrease window size $($c$)$ increase BER

$($d$)$ Increase window size