A machine lengthens a metal cylinder by rolling it under pressure. The radius of the cylinder decreases at a constant rate of 0.

A machine lengthens a metal cylinder by rolling it under pressure. The radius of the cylinder decreases at a constant rate of 0.05 inches per second while the volume stays constant at 128π cubic inches. At what rate is the length L changing when the radius r is 1.8 inches? [Note: V = πr 2L.]