List the members of the following sets. Hint: The keyword is $$list$.$

$($a$)\{$x in N : $12<$ x$2<=70\}$ Hint: In this course, $0$ is an element of N$.$

$($b$)\{$x in Z : $5<$ x$2<=70\}$

$($c$)\{$a$,\{$a$\},\{$a$,$ b$\}\}$