A small spherical insulator of mass 11.810^-2 kg and charge +66 x 10^-8 C is hung by a thread of negligible mass. A charge of -91.2 x 10^-8 C is held 16.6 cm away from the sphere and directly to the right of it, so the thread makes an angle with the vertical. Find the tension in the thread. (k = 9.00 x 10⁹ N.m²/C²)