Write regular expressions for the following languages:

$($a$)$ The set of strings of $0\text{'}$s and $1\text{'}$s whose fifth symbol from the right end is $1.$

$($b$)$ The set of $0\text{'}$s and $1\text{'}$s with at least one pair of consecutive $1\text{'}$s$.$

$($c$)$ The set of all strings of $0\text{'}$s and $1\text{'}$s not containing $101$ as a substring.