Let $\backslash$Sigma $=\{0,1\}$

a$.$ Let A $=\{0$ku$0$k $|$ k $>=1$ and u $\backslash$Sigma $*\}.$ Show that A is regular.

b$.$ Let B $=\{0$k$1$u$0$k $|$ k $>=1$ and u $\backslash$Sigma $*\}.$ Show that B is not regular.