Two identical point charges (q = +9.20 x 10-6 C) are fixed at opposite corners of a square whose sides have a length of 0.400 m. A test charge (q0 = -2.20 x 10-8 C), with a mass of 2.80 x 10-8 kg, is released from rest at one of the corners of the square. Determine the speed of the test charge when it reaches the center of the square.