A very small 3.8 g plastic ball (carrying a charge) is suspended by a 10.4 cm string in a uniform electric field of 21000 N/C, as shown. The...

A very small 3.8 g plastic ball (carrying a charge) is suspended by a 10.4 cm string in a uniform electric field of 21000 N/C, as shown. The acceleration of gravity is 9.81 m/s2 . If the ball is in equilibrium when the string makes a 40◦ angle with the vertical as indi- cated, what is the net charge on the ball?Answer in units of C.