The radius of a circular plate is increasing at the rate of $0.01\;cm/sec$ when the radius is $12\; cm$. Then the rate at which the area increases, is :

Question

\[\begin {array} {1 1} (a)\;0.24\; \pi sq.cm/sec & \quad (b)\;60\;\pi sq.cm/sec \\ (c)\;24\; \pi sq.cm/sec & \quad (d)\;1.2 \pi sq.cm/sec \end {array}\]