Answer:
The rate at which the surface area is changing with respect to time when r = 40 cm is 22400π cm²/min
Not sure if you want it in absolute values since the question says use symbolic notation but if so, multiplying by π gives 70371.675 cm²/min
Explanation:

The surface area of a sphere of radius r is given by:

The rate of change of surface area is given by


We are given that
= 70 cm/min and asked to find rate of change of S when r = 40 cm
Substituting these values into the equation for


In absolute values