Question

When organic waste is dumped into a pond, the oxidation process that takes place reduces the pond's oxygen content. However, given time, nature will restore the oxygen content to its natural level. Suppose the oxygen content t days after organic waste has been dumped into the pond is given by
f(t) = 100 ((t^2 − 4t + 4)/(t^2 + 4))
(0 ≤ t < ∞)
percent of its normal level. When is the rate of oxygen regeneration greatest?