b$)(6$ pts$)$ Suppose we use Selective$-$Repeat with $($sender and receiver$)$ window size of $3$ and

$8-$bit sequence numbers $(0$ to $255),$ over a channel that may corrupt or delay packets

but does not lose or reorder packets. Suppose at some time t$,$ the next in$-$order packet

the receiver is expecting is for sequence number $42.$

$1.(3$ pts$)$ At time t$,$ which ACK numbers that are currently propagating back to

the sender would trigger the sender to advance its window? There are multiple

correct possible answers. List them all and explain. $($Hint: think about the range

of sequence numbers inside the sender$$s window at time t$)$

$2.(3$ pts$)$ At time t$,$ which ACK numbers are currently propagating back to the

sender$?$ There are multiple correct possible answers. List them all and explain.

$($Hint: There are some subtle cases $($e$.$g$.$ involving losses and retransmissions of

data and ACK packets$)$ that are easy to overlook.$)$