Question $4(25$ points$)$

Consider TCP reliable data transfer of letters $A,B,C,D,$ and $E,$ each encoded into four bytes of data and sent in an individual segment from host $x$ to host $Y($there is no payload data traffic from $Y$ to $x).$ The user types a new letter every $0\mathrm{.}5$ seconds. Suppose the first segment carrying A has SeqNumb $=45$ and ACK$=234.$ Suppose the regular one$-$way delay between $x$ and $Y($and vice versa$)$ is $0\mathrm{.}5$ seconds. Suppose all exchanges take the regular delay, but the transmission of letter $B$ from $x$ to $Y$ takes $1\mathrm{.}75$ seconds.

A$.$ Draw the exchanged segments with SegNumb, ACK, and carried data.

B$.$ How large does the Timeout need to be to avoid retransmissions?

C$.$ When is each letter delivered to the application layer at $Y?$