Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
-The decay of $212 \mathrm { mg }$ of an isotope is given by $\mathrm { A } ( \mathrm { t } ) = 212 \mathrm { e } ^ { - 0.02 \mathrm { t } }$ , where $\mathrm { t }$ is time in years. Find the amount left after 28 years.

A) $119 \mathrm { mg }$
B) $121 \mathrm { mg }$
C) $208 \mathrm { mg }$
D) $61 \mathrm { mg }$