$(5$ points$)$

Let $=\{a,b\}.$ Give $($nondeterministic$)$ pushdown automata for the following languages and sufficiently comment how your automata work.

$($a$)L_1=\{win{}^{*}|$#$a(w)=$#$b(w)\}$

$($b$)L_2=\{a^n{b}^m{a}^l|n,m,lin{N}_0,l=n+m^{{?}^{?}}m1\}$