Find context$-$free grammars for the following languages:

$($a$)L=\{\begin{array}{ccc}wx{w}^R\text{:}\text{w}\text{i}\text{n}& \{a,& b{\}}^{**}\\ x\end{array}$ is a terminal symbol not a or $\{$:$b\}($note: $w$ can be $)$

$($b$)L=\{win\{a,b{\}}^{+}$:$n_a(w)=n_b(w)+1\}($note: $n_a$ denotes the number of a$\text{'}$s$,!$inL $)$

$($c$)L=\{a^{2n}{b}^{3n}$:$n0\}$