In a communication network, a node A sends data to node $B,$

the channel between A and $B$ has a data rate of $1000kbps$ and a

propagation delay of $10ms.$ For what frame sizes does stop$-$and$-$

wait give an efficiency of $100\%?$

$($a$)40$kbits

$($b$)100$ kbits

$($c$)50$ kbits

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