Two Small Insulating Spheres Are Attached to Silk Threads and Aligned

Multiple Choice

Two small insulating spheres are attached to silk threads and aligned vertically as shown in the figure.These spheres have equal masses of 40 g,and carry charges q₁ and q₂ of equal magnitude 2.0 μC but opposite sign. The spheres are brought into the positions shown in the figure,with a vertical separation of 15 cm between them.Note that you cannot neglect gravity.(k = 1/4πε₀ = The tension in the lower thread is closest to

A) 1.2 N.
B) 1.4 N.
C) 1.6 N.
D) 1.8 N.
E) 2.0 N.