Assume that for a TCP sender$,$ the congestion window size $c$ nd $=24,$ the slow start threshold ssthresh $=20,$ and there is no timeout or triple duplicate ACKs. What will be the congestion windows size cwnd in the next transmission round, i$.$e$.,$ after one RTT$?($Hint: Since cwnd $$ ssthresh, the sender is in the congestion$-$avoidance phase.$)$

$15$

$1$

$25$

$15$