(c) $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{1}{2}mv^{2} = eV$
$v\ = \sqrt{\frac{2eV}{m}} = \sqrt{2V \times \frac{e}{m}}$
$v = \ \sqrt{2 \times 0.91 \times 1.76 \times 10^{11}}$
$\ \ = 5 \times 10^{5}m/s$
= 500Km/s