a$)$ Let S $=\{$ab bb$\}$ and T $=\{$ab bb bbbb$\}.$ Show that S$*=$

T$*.(4$ Points$)$

b$)$ Let S $=\{$ab bb$\}$ and T $=\{$ ab bb bbb$\}.$ Show that S$*!=$

T$*$ but that S$*$ T$*.(4$ Points$)$

c$)$ What principle does this illustrate? $(2$ Points$)$