Solve the Problem $251 \mathrm{mg}$ Of an Isotope Is Given By $\mathrm{A}(\mathrm{t})=251 \mathrm{e}^{-0.033 \mathrm{t}}$

Multiple Choice

Solve the problem.
-The decay of $251 \mathrm{mg}$ of an isotope is given by $\mathrm{A}(\mathrm{t}) =251 \mathrm{e}^{-0.033 \mathrm{t}}$ , where $\mathrm{t}$ is time in years. Find the amount left after 86 years.

A) 14
B) 243
C) 8
D) 15