A positive charge q₁ = 3.50 C on a frictionless horizontal surface is attached to a spring of force constant k as in the figure shown below. When a charge of

q₂ = 9.450 C

is placed 9.50 cm away from the positive charge, the spring stretches by 5.00 mm, reducing the distance between charges to d = 9.00 cm. Find the value of k.

d k 91 92