4. a) Charge q, and q2 located on the x axis at distance a and -b. find the electric field at the point P, which is at position(0,y) b) If la|=|b|=d, find the electric field at point P, which is at position(0,y). c) if point P located at (0, -co), find the electric field at point P. d) if point P located at (co, 0), find the electric field at point P