Two identical metal spheres each with a mass of 0.1 kg are suspended from the same point by two light threads of equal length. A charge of -2 microcouloumb is placed on the sphere, and a charge of +4 microcoulomb is placed on other sphere. The spheres come to rest with an angle of 30 degrees between the threads. If the threads make an angle of 60 degrees with the vertical, what is the tension in each thread?