Answer
About 8 grams
Work Step by Step
Model: $ A=A_{0}e^{kt}$
$ t=0$ for the year $2010.$
Unknown: $ A $, when $ A_{0}=16, t=5715,k=-0.000121t $
$ A=A_{0}e^{kt}=16e^{-0.000121\cdot 5715}\approx 8.013$
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