Define a language A $=\{$b$,$ dc$,$ da$,$ cab, acd, bb$,$ ac$,$ bbc$,$ cdc$,\backslash$lambda $\}$ over the alphabet $\{$a$,$b$,$c$,$d$\}.$

Sort the strings in A in lexicographical order.

Select two different non$-$empty strings u and v from A and give the string v$($u$$v$)$R$$uR$.$

Define a set S $=\{($x$,$y$)|$ x and y are both in A$,$ x$!=$y$,$ and x and y contain a common non$-$empty suffix$\}.$ Give two elements in S and two elements not in S$.$