a b c d

c

$\text{From Energy Conservation } K_i + U_i = K_f + U_f $ $ K_i = 0 , K_f = k_1 + K_2 = 2K $ $ 0 - \frac{q^2}{4\pi \epsilon_0 r_1} = 2K - \frac{q^2}{4\pi \epsilon_0 r_2} $ $ 2K = \frac{q^2}{4\pi \epsilon_0 r_2} - \frac{q^2}{4\pi \epsilon_0 r_1}= mv^2 $ $ v = 0.3m/s$