In circuit switching technology the length of the line is $100$ km$,$ the

velocity of propagation is $108$ m$/$s and the data rate is $100$ Mbps$.$ The

maximum efficiency for transmitting a message of $5$x$104$ bits is:

$($a$)500\%($b$)100\%($c$)50\%($d$)$ neither a$,$ b or c

$5($a$)($b$)($c$)($d$)$

$6)$ Two communication nodes use the Go$-$Back$-$N ARQ protocol

with a window size of $100.$ The transmitter exhausted its window

before receiving a negative acknowledgment for frame one. In this

case the transmitter needs to:

$($a$)$ retransmit frame one only $($b$)$ retransmit frame $1$ and all

subsequent frames $($c$)$ retransmit frames $1$ and $100$

$($d$)$ neither a$,$ b or c$.$