Coronary arteries are responsible for supplying oxygenated blood to heart muscle. Coronary heat disease is caused by the arteriosclerosis, i.e., the deposition of plaque along the walls of the coronary arteries. The radius of typical open artery is 1.5 mm. In a patient with a "serious" case of coronary arteriosclerosis, plaque may line the walls so that it reduces the radii of the open lumens of these arteries to 0.50 mm.

A. Assuming that all other variables affecting blood flow remain the same, then determine the ratio of blood flow in a patient having the occluded coronary arteries described above vs. a healthy individual having 100% open arteries. Explain your reasoning, and show your calculations.

B. Using the physical relationships described in the Hagen-Poiseuille equation, explain to this patient why his body might try to compensate for the increased resistance in his occluded coronary arteries by an increase in his blood pressure.