Find all strings in $L((ab+b{)}^{**}b(a+ab{)}^{**})$ of length less than four.

Give regular expressions for the following languages.

$($a$)**L_1=\{a^n{b}^m,n3,m4\}.$

$($b$)L_2=\{a^n{b}^m$:

Write regular expressions for the following languages on $\{0,1\}.$

$($a$)$ all strings ending in $10,$

$($b$)$ all strings not ending in $10,$