$4($a$).$ Consider language $L=\{b{a}^{n}b{a}^n|n>0\}$ over alphabet $=\{a,b\}.$ Using Pumping

Lemma prove that this language is not regular.

$($b$)$ Using result of $($a$)$ prove that language $B=\{\begin{array}{c}ww|w\end{array}$ from $\{$:${}^{**}\}$ is not regular. DO

NOT USE PUMPING LEMMA! Use closure properties of regular languages instead.