# Solución

$${{ - 2{t^4} - 2{t^3} + 200t + 50} \over {{{\left( {{t^3} + 50} \right)}^2}}}$$
$−0.02395 \text{ mg/L-hr}$, $−0.01344 \text{ mg/L-hr}$, $−0.003566 \text{ mg/L-hr}$, $−0.001579 \text{ mg/L-hr}$