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**^_^Engineer_Adam^_^** Hello i Need Help on mathematical models

11. The surface area of a sphere is a function of its radius. If $\displaystyle r$ centimeters is the radius of a sphere and $\displaystyle A(r)$ square centimeters is the surface area, then $\displaystyle A(r) = 4 \pi r^2$. Suppose a balloon maintains the shape of a sphere as it is being inflated so that the radius is changing at a constant rate of 3 centimeters per second. If $\displaystyle f(t)$ centimeters is the radius of the balloon after $\displaystyle t$ seconds, do the following:

a.) Compute $\displaystyle (A \circ f)(t)$ and interpret your result.