Points A and B lie within a region of space where there is a uniform electric field that has no x- or z-component; only the y-component Ey is non zero. Point A is at y=8.00 cm and point B is at y=15.0 cm. The potential difference between B and A is VB−VA=+12.0 V, so point B is at higher potential than point A. (a) Is Ey positive or negative? (b) What is the magnitude of the electric field? (c) Point C has coordinates x=5.00 cm, y=5.00 cm. What is the potential difference between points B and C?