Answer
$\pi\frac{16}{9}t^6.$
Work Step by Step
$S(r)=4\pi r^2$ and $r(t)=\frac{2}{3}t^3$.
Therefore $S(r(t))=4\pi \left(\frac{2}{3}t^3\right)^2=\pi\frac{16}{9}t^6.$
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