A. A dipole is formed by placing a positive charge of 8 nC at z = -0.5m and a negative charge of -8 nC at z = 0.5m, on the z-axis. Determine the potential and electric field at x 15 cm on the x-axis. B. A line charge exists on the x-axis from x = 0 to x = d. The linear charge density p is constant. Find the electric potential at points x < 0 on the x-axis.