Find $\underset{x}{lim}h(x),$ if it exists. $($If an answer does not exist, enter DNE.$)$

$f(x)=9x^3-4$

$($a$)h(x)=\frac{f(x)}{x^2}$

$\underset{x}{lim}h(x)=$

$($b$)h(x)=\frac{f(x)}{x^3}$

$\underset{x}{lim}h(x)=$

$($c$)h(x)=\frac{f(x)}{x^4}$

$\underset{x}{lim}h(x)=$