54. We use P
cond
= kA(T
H
− T
C
)/L. The temperature T
at a depth of 35.0 km is
T
=
P
L
kA
+ T
(54.0
× 10
−3
W/m
2
)(35.0
3
m)
2.50 W/m
·K
+ 10.0
◦
C = 766
C .