There lies a section through 2 long concentric cylinders of radii 4.5 and 8 cm. The cylinders have equal and opposite charges per unit length of 2 C/m. Along the common axis runs a wire with an equal positive charge per unit length. Find E at a radial distance r = 0.3 cm. I'm not exactly sure how to complete this problem. I've calculated it ignoring the cylinders, thinking that their charges cancel each other out, yet this was still the incorrect answer. I've also tried this by adding up all of the forces from the cylinders at the point .3 cm, but yet this still didn't work! Any help would be greatly appreciated.