Use the Following to Answer Questions

Use the following to answer questions :
Due to a lightening strike, a forest fire begins to burn and is spreading outward in a shape that is roughly circular. The radius of the circle is modeled by the function r(t) = 3t, where t is the time in minutes and r is measured in meters.
-Write a function for the area burned by the fire directly as a function of t by computing (A ◦ r) (t) .

A) (A ◦ r) (t) = 3πt²
B) (A ◦ r) (t) = 9πt²
C) (A ◦ r) (t) = 6πt
D) (A ◦ r) (t) = 3π²t²