The volume V of a sphere changes with time according to the equation:

$\displaystyle V=35\pi + \pi t^2$

Find the rate of change of the surface area of sphere when t=1sec ?

Am solving problems for fun

and i really stopped at this one

ok $\displaystyle S=4 \pi r^2$

and $\displaystyle V=\frac{4}{3} \pi r^3$

the problem here is that there is no value for r in the problem

I need a start please