Four point charges are held fixed in space on the corners of a rectangle with a length of 20 [cm] (in the horizontal direction) and a width of 10 [cm] (in the vertical direction). Starting with the top left corner and going clockwise, the charges are q₁=+10 [nC] , q₂=10[nC] , q₃=5[nC] , and q₄=+8[nC] . a) Find the magnitude and direction of the electric force on charge q₄ b) Find the magnitude and direction of the electric field at the midpoint between q₃ and q₄ c) Find the magnitude and direction of the electric field at the center of the rectangle.