In general, one can obtain the volume of a sphere and a cube using the formulas below
![\begin{gathered} V_(cube)=l^3 \\ l\rightarrow\text{ side of the cube} \\ V_(sphere)=(4)/(3)\pi r^3 \\ r\rightarrow\text{ radius} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/t66yww7y36vjifhm1ugsc8cc4s8sy8765m.png)
In our case, we need to subtract the volume of the hollow sphere from the volume of the cube, as shown below
![\begin{gathered} V_(cube)=18^3 \\ and \\ V_(sphere)=(4)/(3)\pi(9)^3 \\ \Rightarrow V_(foam)=V_(cube)-V_(sphere) \\ \Rightarrow V_(foam)=2778.371... \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/aexnmu4xgxdjvcy509kpcihvv2j2520tlu.png)
Rounding to the nearest hundredth,
![\Rightarrow V_(foam)\approx2778.37](https://img.qammunity.org/2023/formulas/mathematics/high-school/x4v1mjljnxbaqum7nd9srey83l5hxn6rxs.png)
The answer is 2778.37in^3