''m' represents radius of the circle.
Substitute m(t) into Area function.
[tex]A = \pi m^2 \\ \\ A = \pi (10t)^2 \\ \\ A = 100\pi t^2[/tex]
Now you have Area as function of time.
part B) sub t= 3 to find Area after 3 minutes.
[tex]A(3) = 100\pi (3^2) = 900 \pi[/tex]
