Sound travels as an expanding sphere away from its point of origin. The surface area of a sphere is described by the equation: A = 4an If sound travels through a nonuniform medium its speed is not constant (ie., the rate of change of the radius is non-linear). In a certain non-uniform medium the following equation describes the radius as a function of time: r(t) = 4t3 2t2 + 8t A) Determine the rate of change of the surface area of the sound sphere with respect to radius. B) Determine the rate of change of radius with respect to time. 0) Determine an expression for the rate of change of surface area of the sound sphere with respect to time. D) Find the rate of change of the surface area of the sound sphere 3 seconds after the sound was produced