If the volume of a spherical ball is increasing at the rate of $\;4 \pi \;cc/sec\;$ , then the rate of increase of its radius (in cm/sec) , when the volume is $\;288 \pi\;cc\;$ , is :

Question

$(a)\;\large\frac{1}{6}\qquad(b)\;\large\frac{1}{9}\qquad(c)\;\large\frac{1}{36}\qquad(d)\;\large\frac{1}{24}$