A Brass Wire (D = 2 $19.5 \times 10^{-6} /{ }^{\circ} \mathrm{C}$

A brass wire (d = 2.0 mm, E = 110 GPa) is pretensioned to T = 85 N. The coefficient of thermal expansion for the wire is $19.5 \times 10^{-6} /{ }^{\circ} \mathrm{C}$ . The temperature change at which the wire goes slack is
Approximately: (A) $+5.7^{\circ} \mathrm{C}$
(B) $-12.6^{\circ} \mathrm{C}$
(C) $+12.6^{\circ} \mathrm{C}$
(D) $-18.2^{\circ} \mathrm{C}$