Answer:
[tex]V(t)=0.0112\pi t^{2}[/tex]
Step-by-step explanation:
we have
[tex]V(r)=0.07\pi r^{2}[/tex] -----> equation A
[tex]r(t)=0.4t[/tex] -----> equation B
To find out (V of r)(t) substitute equation B in equation A
[tex]V(r(t))=V(t)[/tex]
[tex]V(t)=0.07\pi (0.4t)^{2}[/tex]
[tex]V(t)=0.07\pi (0.16)t^{2}[/tex]
[tex]V(t)=0.0112\pi t^{2}[/tex]