Two infinite vertical planes of charge are parallel to each other and are separated by a distance d = 4 m. Find the electric field to the left of the planes, to the right of the planes, and between the planes

(a) When each plane has a uniform surface charge density σ = +3 μC/m² and

(b) When the left plane has a uniform surface charge density σ = +3 μC/m² and that of the right plane is σ = –3 μC/m². Draw the electric field lines for each case.