The diagram below shows four charges at the corners of a square of sides d = 1.30 m. Here, q1 = q2 = −q and q3 = 3.0q, where q = 2.30 nC and q3 is located at the origin. What is the force on the fourth charge q4 = 3.50 nC? Assume that the +x axis is directed to the right and the +y axis is directed up. Express your answer in vector form. Do not enter units in your expression. F→ = N