3.21 A line charge of infinite length (L-) above an - - - - --> Z infinite ground plane as shown. The charge density a on the line is uniform. (a) Find the electric potential L at a point (x, y, z) above ground by integrating . P(x, y, z ) 2 Coulomb point charges along the line. (b) From the electric potential, calculate the electric field at that O same location (x, y, z) by taking the gradient of the potential