$($a$)$ What are the standard ports for HTTP$,$ FTP$,$ SMTP$,$ POP$3?(2)($b$)$ Explain with examples, the syntax and the meanings of A$,$ MX$,$ NS and PTR resource records in a DNS database. $(4)($c$)$ Explain with an illustrative example, the working of iterative name resolution. $(3)($d$)$ Explain the reverse resolution mechanism for DNS$.(3)($e$)$ Construct a simple SMTP session to illustrate the working of the SMTP commands. $(3)($f$)$ Construct a simple POP$3$ session to illustrate the working of the POP$3$ commands; what's the main difference between POP$3$ and IMAP? $(3)($g$)$ Outline the working principle of base$64$ encoding; why is it needed? $4($h$)$ What are the important steps in writing a socket program for a TCP client using the Berkley Socket API? $(3)($i$)$ Explain the structure and function of the HTTP GET, POST, and PUT commands. $(4)$