2 small spheres with mass m = 15.1 g are hung by silk threads of length L = 1.21 m from a common point. When the spheres are given equal charges, so that q_1 = q_2 = q, each thread hangs at an angle theta = 26 degrees from the vertical. Find the magnitude q.
Use 9.81 m/s^2 as the acceleration due to gravity and 8.85 * 10^-12 C^2/Nm^2 as the permittivity of free space.