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In a hollow fiber hemodialyzer, blood flows from an artery through the insides of a bundle of cellulose acetate fibers, and a dialyzing fluid (consisting of water and a few dissolved salts) flows on the outside of the fibers. Water and waste products, such as urea, pass through the walls of the fibers, and the slightly purified blood returns to a vein. Consider a patient who is experiencing kidney failure that is connected to such a device. Blood enters from the arterial side at a flow rate of 200mL/min with a urea concentration of 2.1mg/mL. Blood returns to the vein at a flow rate of 195mL/min with a urea concentration of 1.2mg/mL. Assume the dialysate enters the hemodialyzer at a flow rate of 1500mL/min (with no urea initially present). Determine the (A) the rate of urea removal, and (B) the concentration of urea in the dialysate leaving the hemodialyzer. (Ans: A =186mg/min)