Air is being pumped into a spherical balloon so that its volume increases at a rate of $30 \mbox{cm}^3\mbox{/s}$. How fast is the surface area of the balloon increasing when its radius is $13 \mbox{cm}$? Recall that a ball of radius $r$ has volume $\displaystyle V=\frac{4}{3}\pi r^3$ and surface area $S=4\pi r^2$.