Two identical point charges (q = +8.70 x 10^-6 C) are fixed at opposite corners of a square whose sides have a length of 0.670 m. A test charge (q₀ = -2.40 x 10^-8 C), with a mass of 1.30 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.