Q15 This question contains multiple parts. Make sure to read all the instructions and answer each part. Two concentric metal conducting spheres are shown in the figure below - they are positioned to have a common center point. The inner sphere has radius a and is positively charged with +Q, while outer sphere has radius b and is negatively charged with -Q. The figure below shows a cutout cross section of the two concentric conducting spheres. Let r represent the distance from the center of the spheres. Image size: s M L Max Part a (1 points) What is the electric field inside the inner sphere at the very center, at a radial distance r = 0? Select the correct answer O infinite O - ATTEN ON ATEN BY O zero Part b (1 points) What is the electric field between the two spheres, at a radial distance r, where a b? Select the correct answer 2 O infinite O ATER a O O zero O