$7)$ If a communication network uses Selective Reject ARQ protocol,

the probability of receiving the first frame in error depends on:

$($a$)$ Both frame length and BER $($b$)$ frame length only

$($c$)$ BER only

$($d$)$ neither a nor b not c

$($a$)$

$($b$)$

$($c$)$

$($d$)$

$8)$ Two stations in a bus topology use frames of $1000-$bits. The

propagation time between the two stations is the same as the

transmission time.

If the two stations use stop$-$and$-$wait, what will be the maximum line

efficiency?

$($a$)50\%$

$($b$)33$

$($c$)100\%$

$($d$)33\%$

$8\mathrm{.}1$

$($a$)$

$($b$)$

$($c$)$

$($d$)$