Problem $3[12$ points$]$ Short answer questions on port numbers.

$($a$)$ Consider a TCP connection between Host A and Host B$.$ Suppose that the TCP segments traveling from Host A to Host B have source port number $1,200$ and destination port number $1,500.$ What are the source and destination port numbers for the segments traveling from Host B to Host A$?$

$($b$)$ Suppose a process in Host C has a UDP socket with port number $6,789.$ Suppose both Host A and Host B each send a UDP segment to Host C with destination port number $6,789.$ Will both of these segments be directed to the same socket at Host C$?$ If so$,$ how will the process at Host C know that these two segments originated from two different hosts?

$($c$)$ Find the "well$-$known" port numbers used by the File Transfer Protocol $($FTP$).$ You may use online resources with proper citations.

$($d$)$ Suppose that a Web server runs in Host C on port $80.$ Suppose this Web server uses persistent connections, and is currently receiving requests from two different Hosts, A and B$.$ Are all of the requests being sent through the same socket at Host C$?$ If they are being passed through different sockets, do both of the sockets have port $80?$ Discuss and explain.