help please

When a certain medical drug is administered to a patient,

the number of milligrams remaining in the patient's bloodstream after t hours is modeled by

D(t) = 70e−0.5t.

How many milligrams of the drug remain in the patient's bloodstream after 3 hours?

(Round your answer to one decimal place.)

$\begin{array}{|rcll|} \hline D(t) &=& 70e^{-0.5t} \quad & | \quad t = 3\ hours \\ D(3) &=& 70e^{-0.5\cdot 3} \\ D(3) &=& 70e^{-1.5} \\ D(3) &=& 70\cdot 0.22313016015 \\ D(3) &=& 15.6191112104\ mg \\ \hline \end{array}$

There are 15.6 mg of the drug remain in the patient' bloodstream after 3 hours.