A$-$to$-$B data link layer communications channel has a bit rate of $4$Kbps$,$ A$-$to$-$B propogation delay $20$ msec, B$-$to$-$A delay the same, frame size $160$ bits and stop$-$and$-$wait $($that is$,1-$bit sliding window, Protocol $4)$ protocol is used.

$($i$)$ Assuming simplex data channel, that is no reverse data traffic, immediate individual ack and ignorable ack transmission time, compute the channel utilization. Show your work.