51. We use Eq. 27-17: ρ
− ρ
0
= ρα(T
− T
), and solve for T :
T = T
+
1
α
ρ
− 1
= 20
◦
C +
4.3
× 10
−3
/K
58Ω
50 Ω
= 57
C .
We are assuming that ρ/ρ
= R/R
.