\text { Four point charges } q_{1}=13 \mu \mathrm{C}, q_{2}=-3.5 \mu \mathrm{C}, q_{3}=-6 \mu \mathrm{C}, \text { and } q_{4}=8 \mu \mathrm{C} \text { are located at all } corners

of a rectangle as shown in figure. If a = 10 m, and b= 6 m then: A. Find the electric field at point (P) at the center. B. If a point charge q =– 15 µC is placed on point P,find the electric force exerted on it and the direction angle