4. The flux through Arizona is
Φ =
−B
r
A =
−(43 × 10
−6
T)(295, 000 km
2
)(10
3
m/km)
2
=
−1.3 × 10
7
Wb ,
inward. By Gauss’ law this is equal to the negative value of the flux Φ
through the rest of the surface
of the Earth. So Φ
= 1.3
× 10
7
Wb, outward.