Two small spherical balls whose charges are $20 \mu c$ each are hanged with help of 1 m long thread from roof. In equilibrium both threads are seperated by $ 60^{\circ}$ Tension in each thread is :

Question

$(A)\;36 \;N \\ (B)\;72 N \\ (C)\; 7.2 N \\ (D)\;0.72 N $