13. The number density of free electrons in a conducting material is about 8.4×10<sup>28</sup> m<sup>-3</sup>. If a
current flows in a wire made of that material with a circular cross-section of diameter 1.0 mm
(1 mm = 0.001 m), and the drift speed of the electrons carrying the current is 8.28 cm/hr (1 cm
= 0.01 m, 1 hr = 3600 s), how long does it take for 1.0 C to pass through any point in the wire?
A. 4.1 s
B. 11 s
C. 0.036 s
D. 1.0 s