Concept Simulation 11.1 reviews the concept that plays the central role in this problem. (a) The volume flow rate in an artery supplying the brain is 4.3×10−6 m3 /s. If the radius of the artery is 4.2 mm, determine the average blood speed. (b) Find the average blood speed as a constriction in the artery if the constriction reduces the radius by a factor of 2. Assume that the volume flow rate is the same as that in part (a). (a) Number Units (b) Number Units