Health/Medicine. During the course of treatment of an illness, the concentration of a dose of a drug (in $\mathrm{mcg} / \mathrm{mL}$ ) in the bloodstream fluctuates according to the model
$$ C(t)=60-0.75 t^{2} $$
where $t=0$ is when the drug was administered. Assuming a single dose of the drug is administered, in how many hours (to the nearest hour) after being administered will the drug be climinated from the bloodstream?