Answer: 1118 K

$\Delta G^\circ = \Delta H^\circ - T \Delta S^\circ$

Since, $\Delta H^\circ$ is +ve and $T\Delta S$ is also +ve, for $\Delta G^\circ$ to be -ve.

$T\Delta S^\circ > \Delta H^\circ i.e., T > \frac{\Delta H^\circ}{\Delta S^\circ}$

i.e., $\frac{179100 J}{160.2J/K} > 1118 $ K