question 8. help me understand better the question and its solution please explain step by step do not skip parts

ANSWER
[tex]\begin{equation*} 0.36\text{ mg} \end{equation*}[/tex]EXPLANATION
The given function is:
[tex]D(h)=6e^{-0.7h}[/tex]To determine the amount of the drug that is in the patient after 4 hours, we have to solve for D when h is equal to 4. That is:
[tex]\begin{gathered} D(4)=6e^{-0.7*4} \\ \\ D(4)=6e^{-2.8} \\ \\ D(4)=6*0.06081 \\ \\ D(4)=0.36\text{ mg} \end{gathered}[/tex]That is the answer to two decimal places.