Answer is: spontaneous in the reverse direction at all temperatures.
Spontaneity can be determined using the change in Gibbs free energy:
ΔG = ΔH - TΔS.
ΔG changes in Gibbs free energy.
ΔH changes in enthalpy.
ΔS changes in entropy.
T is temperature.
When ΔS < 0 (negative entropy change) and ΔH > 0 (endothermic reaction), the process is never spontaneous (ΔG> 0), but the reverse process is always spontaneous.