A parabolic listening device is shaped such that the depth of the bowl depends on its radius and can be represented by the curve D(r) = 0.145r^2.
What is the radius when the depth is 8 inches? Round to the nearest thousandth of an inch.

1) 4.417 inches
2) 5.252 inches
3) 7.428 inches
4) 20.505 inches