The circumference of a circle is computed as follows:
[tex]C=2\pi r[/tex]Solving for r, and replacing with C = 5, we get:
[tex]\begin{gathered} 5=2\pi r \\ \frac{5}{2\pi}=r \\ 0.8m\approx r \end{gathered}[/tex]The volume of a sphere is computed as follows:
[tex]V=\frac{4}{3}\pi r^3[/tex]Substituting with r = 0.8, we get
[tex]\begin{gathered} V=\frac{4}{3}\pi\cdot0.8^3 \\ V\approx2.1m^3 \end{gathered}[/tex]