87.
E
×
B = µ
0
S, where
E = E ˆ
k and
S = S(
−ˆj). One can verify easily that since ˆk × (−ˆi) = −ˆj,
B has to
be in the negative x direction. Also,
B =
c
=
100 V/m
3.0
× 10
8
m/s
= 3.3
−7
T .