$(1$ point$)$ A drug is injected into the bloodstream of a patient. The concentration of the drug in the bloodstream $($in milligrams per cubic centimeter$)t$ hours after the injection is given by

$C(t)=\frac{0\mathrm{.}16t}{t^2+3}$

Find the instantaneous rate of change of the drug concentration with respect to time at the following times:

$($A$)C^{\text{'}}(\mathrm{.}5)=$

$($B$)C^{\text{'}}(3)=$