Consider the concentration, C$,($in mg$/$liter$)$ of a drug in the blood as a function of the amount of drug given, x$,$ and the time since injection, t$.$ For $0<$ x $<4$ mg and t $0$ hours, we have

C $=$ f$($x$,$ t$)=30$te $(1-$x$)$t

f $(2,4)=$

$0\mathrm{.}0402$

Give a practical interpretation of your answer: f$(2,4)$ is

$$the amount of a $2$ mg dose in the blood $4$ hours after injection.

$$the amount of a $4$ mg dose in the blood $2$ hours after injection.

$$the change in concentration of a $2$ mg dose in the blood $4$ hours after injection.

$$the concentration of a $4$ mg dose in the blood $2$ hours after injection.

$$ E$.$ the concentration of a $2$ ma dose in the blood $4$ hours after injection.

F$.$ the change in concentration of a $4$ mg dose in the blood $2$ hours after injection.