For Point defect (vacancy), we have the following relation

$n=N\times exp\Bigg(\dfrac{-Ev}{KT}\Bigg)\\ $

$\therefore \ \dfrac{n}{N}=e^{\dfrac{-Ev}{KT}}\\$ Using  $K=1.38\times 10^{-23}\ \dfrac{J}{K}\ \ \ \ \ \ \ \ E_v=1.8\times 1.6\times 10^{-19}$ 1) For $t_1=-119^{\circ}\ C=-119+273=154\ K$ $\therefore \ \dfrac{n}{N}=\dfrac{e^{-(1.8\times 1.6\times 10^{19})}}{1.38\times 10^{-23}\times 154}=e^{-153.51}=1.4084\times 10^{-59}$ **.............(Answer)** **2) For $t_2=80^{\circ}\ C=80+273=353\ K$** $\therefore \ \dfrac{n}{N}=\dfrac{e^{-(1.8\times 1.6\times 10^{19})}}{1.38\times 10^{-23}\times 353}=e^{-59.12}=2.11\times 10^{-26}$