11. We use v
d
= J/ne = i/Ane. Thus,
t
=
L
v
i/Ane
LAne
i
(0.85 m)(0.21
× 10
−4
m
2
)(8.47
28
/ m
3
)(1.60
−19
C)
300 A
8.1
s = 13 min .