A heart attack victim is given a blood vessel dilator to increase the radii of the blood vessels. After receiving the dilator, the radii of the affected blood vessels increase at about 3% per minute. According to Poiseulle's law, the volume of blood flowing through a vessel and the radius of the vessel are related by the formula V = kr4 where k is a constant. What will be the percentage rate of increase in the blood flow after the dilator is given?
◦ 12%/min
◦ 9%/min
◦ 18%/min
◦ 15%/min