In the human body, blood vessels can dilate, or increase their radii, in response to various stimuli, so that the volume flow rate of the blood increases. Assume that the pressure at either end of a blood vessel, the length of the vessel, and the viscosity of the blood remain the same, and determine the factor R(dilated)/R(normal) by which the radius of a vessel must change in order to double the volume flow rate of the blood through the vessel.