Three positive point charges are located at the corners of a rectangle. Find the electric field at the fourth corner if q1 = 5 nC,
q2 = 6 nC, and q3 = 7 nC. The distances are d1 = 0.6 m and d2 = 0.2 m. (Let the positive x-direction be to the right, and the positive y-direction be upward.)