The radius of a circular oil slick expands at a rate of 3 m/min.

(a) How fast is the area of the oil slick increasing when the radius is 22 m?

$\frac{dA}{dt} =$ $m^2/min$

(b) If the radius is 0 at time $t=0$, how fast is the area increasing after 4 mins?

$\frac{dA}{dt} =$ $m^2/min$