An Alpha Particle (A Helium Nucleus, Having Charge +2e and Mass

An alpha particle (a helium nucleus, having charge +2e and mass 6.64 × 10^-27 kg) moves head-on at a fixed gold nucleus (having charge +79e) . If the distance of closest approach is 2.0 × 10^-10 m, what was the speed of the alpha particle when it was very far away from the gold? (k = 1/4πε₀ = 9.0 × 10⁹ N ∙ m²/C², e = 1.60 × 10^-19 C)

A) 2.3 × 10⁵ m/s
B) 4.6 × 10⁵ m/s
C) 2.3 × 10⁶ m/s
D) 4.6 × 10⁶ m/s