Oxygen reacts with solid glycylglycine C₄H₈N₂O₃ to form urea CH₄N₂O, carbon dioxide, and water: 

3O₂(g) + C₄H₈N₂O₃(s) ⇋ CH₄N₂O(s) + 3CO₂(g) + 2H₂O(l)

At T = 298 K and 1.00 atm, solid glycylglycine has the following thermodynamic properties:

ΔG^o_f = −491.5 kJ mol⁻¹, ΔH^o_f = −746.0 kJ mol⁻¹, S° = 190.0 J K⁻¹ mol⁻¹

Calculate ΔG^o_R at T = 298.15 K and at T = 310.0 K. State any assumptions that you make.