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

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.