Calculate the ionic conductivity at 300 K for an ionic crystal. Assume 6 × 10²0 Schottky defects per cubic meter, an activation energy of 0.8 eV and D0 = 10⁻³ m²/s.

a) 4.82 × 10⁻⁴ S/m
b) 6.73 × 10⁻⁴ S/m
c) 8.29 × 10⁻⁴ S/m
d) 9.91 × 10⁻⁴ S/m