Oil is poured on a flat surface, and it spreads out forming a circle. The area of this circle is increasing at a constant rate of 5 cm 2 /s.

Oil is poured on a flat surface, and it spreads out forming a circle.

The area of this circle is increasing at a constant rate of 5 cm2/s.

At what rate, in cm/s, is the radius of the circle increasing when the radius is 5 cm?

A. 1/2pi

B. 1/pi

C. 1

D. pi

E. 2pi