Solve the Problem $\mathrm { D } ( \mathrm { h } ) = 6 \mathrm { e } ^ { - 0.4 \mathrm {~h} }$

Multiple Choice

Solve the problem.
-The function $\mathrm { D } ( \mathrm { h } ) = 6 \mathrm { e } ^ { - 0.4 \mathrm {~h} }$ can be used to determine the milligrams $\mathrm { D }$ of a certain drug in a patient's bloodstream h hours after the drug has been given. How many milligrams (to two decimals) will be present after 9 hours?

A) $4.02 \mathrm { mg }$
B) $0.16 \mathrm { mg }$
C) $219.59 \mathrm { mg }$
D) $0.82 \mathrm { mg }$