A stone dropped into a still pond sends out a circular ripple whose radius increases at a constant rate of 2.1 ft/s.

(a) How rapidly is the area enclosed by the ripple increasing when the radius is 5 feet?

The area is increasing at (ft^2)/s

(b) How rapidly is the area enclosed by the ripple increasing at the end of 9.4 seconds?

The area is increasing at (ft^2)/s