regular expression defining each of the following languages over the alphabet $\backslash$Sigma $=\{$a$,$ b$\}.$

$($a$)$ L $=\{$aab$,$ ba$,$ bb$,$ baab$\}$;

$($b$)$ The language of all strings containing exactly two b$\text{'}$s$.$

$($c$)$ The language of all strings containing at least one a and at least one b$.$

$($d$)$ The language of all strings that do not end with ba$.$

$($e$)$ The language of all strings that do not containing the substring bb$.$

$($f$)$ The language of all strings in which every b is followed immedia