Three 250 μC Charges Are Placed on Tiny Conducting Spheres at at the Ends

Multiple Choice

Three 2.50 μC charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120° angles as shown below. The magnitude, in N, of the force on the knot at the center is

A) 0.
B) 3.75 × 10−².
C) 5.63 × 10−².
D) 6.50 × 10−².
E) 7.50 × 10−².