A potter forms a piece of clay into a right circular cylinder. As she rolls it, the height $h$ of the cylinder increases and the radius $r$ decreases. Assume that no clay is lost in the process. Suppose the height of the cylinder is increasing by $0.2$ centimeters per second. What is the rate at which the radius is changing when the radius is $5$ centimeters and the height is $6$ centimeters?

(Include help (units) with your answer.)