The surface area S (in square meters) of a hot-air balloon is given by S(r)=4(pi)r^2 where r is the radius of the balloon (in meters). If the radius r is increasing with time t (in seconds) according to the formula r(t)=(2/3)t^3, find the surface area S of the balloon as a function of time t.I-I am so proud of myself for getting that right. Without ( Read more... )