The electrostatic potential v(x, y) in free space in a region where the charge densityp is zero is given by v (x.y)=4e* +fr)-3y2. given that the x-component of

The electrostatic potential V(x, y) in free space in a region where the charge densityp is zero is given by V (x.y)=4e* +fr)-3y2. Given that the x-component of the electrie field Ex, and V are zero at the origin, f(x) is (a) 3x-4e" +8x (c) 4e*-8 (b) 3x-4e" +16x (d) 3xs4e"