Find the derivative of $f(y) = \frac{20 \cdot 4 \sqrt[4]{y}}{\ln(y)}$.
Enclose arguments of functions, numerators, and denominators in parentheses. For example, $\sin(2x)$ or $(a - b)/(1 + n)$. Include a multiplication sign between symbols. For example, $a \cdot \pi$.
f'(y) =