Gibbs Free Energy and Spontaneity

For the reaction N2(g) + 3H2(g) → 2NH3(g) at 298 K, given ΔH° = -92.4 kJ/mol and ΔS° = -198.3 J/(mol·K): (a) Calculate ΔG° at 298 K. (b) Is the reaction spontaneous at 298 K? (c) At what temperature does the reaction become non-spontaneous? (d) Explain why this reaction is favored at low temperatures but not high temperatures.