A charge Q = -610 NC (-6.1 × 10^-7 C) is uniformly distributed on a ring of 2.4-m radius. A point charge q = +480 nC (+4.8 × 10^-7 C) is fixed at the center of the ring, as shown in the figure. An electron is projected from infinity toward the ring along the axis of the ring. This electron comes to a momentary halt at a point on the axis that is 5.0 m from the center of the ring. What is the initial speed of the electron at infinity? (e = 1.60 × 10^-19 C, k = 1/4πε_0 = 8.99 × 10^9 N · m^2/C^2, m_e = 9.11 x 10-31 kg)

Question

A charge Q = -610 NC (-6.1 × 10^-7 C) is uniformly distributed on a ring of 2.4-m radius. A point charge q = +480 nC (+4.8 × 10^-7 C) is fixed at the center of the ring, as shown in the figure. An electron is projected from infinity toward the ring along the axis of the ring. This electron comes to a momentary halt at a point on the axis that is 5.0 m from the center of the ring. What is the initial speed of the electron at infinity? (e = 1.60 × 10^-19 C, k = 1/4πε_0 = 8.99 × 10^9 N · m^2/C^2, m_e = 9.11 x 10-31 kg)
a. 2.2 × 10^6 m/s
b. 3.4 × 10^6 m/s
c. 6.6 × 10^6 m/s
d. 1.1 × 10^6 m/s
e. 4.5 × 10^6 m/s

Apparently, the correct answer to this question is 6.6 × 10^6 m/s. I saw a solution on how that answer is achieved, but despite following all the steps exactly, I ended up with a completely different answer. I don't know what I am doing wrong and it is frustrating me.