Solution:
The formula for half-life is given below as
[tex]N(t)=N_0(\frac{1}{2})^{\frac{t}{\frac{t1}{2}}}[/tex]Where the given values are
[tex]\begin{gathered} N_0=2076g \\ t=20years \\ t^{\frac{1}{2}}=5years \end{gathered}[/tex]By substituting the values, we will have
[tex]\begin{gathered} N(t)=N_{0}(\frac{1}{2})^{\frac{t}{\frac{t\times1}{2}}} \\ N(t)=2076\times(\frac{1}{2})^{\frac{20}{5}} \\ N(t)=2076\times(\frac{1}{2})^4 \\ N(t)=\frac{2076}{16} \\ N(t)=129.75g \end{gathered}[/tex]Hence,
The final answer is
[tex]\Rightarrow129.75g[/tex]