Clevis and Pin $\left( d _ { p } = 15 \mathrm {~mm} \right)$

$\text { A steel rod } \left( E _ { s } = 210 \mathrm { GPa } , d _ { r } = 12 \mathrm {~mm} , \text { cte } _ { s } = 12 \times 10 ^ { - 6 } / { } ^ { \circ } \mathrm { C } \right) \text { is held stress-free between rigid walls by a }$ clevis and pin $\left( d _ { p } = 15 \mathrm {~mm} \right)$ assembly at each end. If the allowable shear stress in the pin is $45 \mathrm { MPa }$ and the allowable normal stress in the rod is $70 \mathrm { MPa }$ , the maximum permissible temperature drop $\Delta T$ is approximately:

A) $14 ^ { \circ } \mathrm { C }$
B) $20 ^ { \circ } \mathrm { C }$
C) $28 ^ { \circ } \mathrm { C }$
D) $40 ^ { \circ } \mathrm { C }$