A certain cylindrical wire carries current. We draw a circle of radius r around its central axis in Figure {:1} to determine the current i within the circle. Figure {b} shows current i as a function of r2. The vertical scale is set by is = 4.0 mA, and the horizontal scale is set by r52 = 5.4 mm2. [a] Is the current density uniform? [b] If so, what is its magnitude? (ri'l [bl Number n Units V