$4.$ Find s$-$grammars for the following languages:

$($a$)$ Find an s$-$grammar for L$($aa$^*$ cc$+$bb$^*$ cc$).[5$ pts$]$

$($b$)$ Find an s$-$grammar for L$=\{$a$^$n b$^($n$+2)$:n$>=1\}.[5$ pts$]$