# The radius of a circle is increasing uniformly at the rate of $3\; cm/s.$ Find the rate at which the area of the circle is increasing when the radius is $10\; cm$.
$\begin{array}{1 1}(A)\;60\pi cm^2/s \\ (B)\;30\pi cm^2/s \\(C)\;20\pi cm^2/s \\(D)\;40\pi cm^2/s \end{array}$