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Which of the following is NOT equivalent to $\cfrac{d}{dx} \left(\sqrt[3]{x}\right)$ evaluated at $x=8$?

$\lim \limits_{x \to 8} \cfrac{\sqrt[3]{x}-2}{x-8}$

$\lim \limits_{h \to 0} \cfrac{\sqrt[3]{x+h}-\sqrt[3]{x}}{h}$

$\cfrac{1}{12}$

$\cfrac{1}{6}$