see the pic attached

Remaining Time: 76:21:25 A spherical snowball is melting in the sun. It is noted that its surface area decreases at a rate of 5 cm / s at the moment when its diameter is - cm. The goal here is to determine the rate at which the diameter varies at that same moment. To solve this problem, let r be the diameter of the snowball in cm, A its surface area in cm , and t the time in seconds (s). (a) Express A as a function of c . (The surface area is a formula you can find in your textbook.) A cm2 dA (b) What is the value of when a - ? Give the exact value. dA dr (c) Using our previous results, give the (exact) value of dt when c = - cm. Beware of signs, remember that the surface area of the snowball is decreasing with time! si cm/s. dt