ty d +2 # (c) Through an infinite charged plate described in part (a), an infinitely long cylin- drical cavity of radius d is drilled so that it is coaxial with the y axis, as shown in the figure. [The system consists of a plate from part (a) with the cylinder from part (b) taken away.] The plate (with the cavity) still carries the same uniform current density J = Joy- Using the principle of superposition, and relying on the answers from parts (a) and (b), explain in words how we can get the magnetic field at an arbitrary point. (d) For the points on the a axis (namely z = 0,y = 0), calculate B,(z). Roughly graph B.(x), including also I