An infinite plane of uniform surface charge density σ = +4.5 nC/m² lies in the y = 2.00 m plane, and a second infinite plane of uniform surface charge density σ = -4.5 nC/m² lies in the y = 0 m plane. Find the magnitude of the electric field at (a) y = 1.00 m, (b) y = 3.00 m, and (c) y = -1.00 m. (modified from Tipler & Mosca, 2007, Example 22-8)