Two identical point charges (q = +7.25 10-6 C) are fixed at diagonally opposite corners of a square with sides of length 0.485 m. A test charge (q0 = -2.60 10-8 C), with a mass of 7.05 10-8 kg, is released from rest at one of the empty corners of the square. Determine the speed of the test charge when it reaches the center of the square.