How can calculate the standard free energy change

Question

At 25^oC the substance X is an element which has the elemental form of X(s). At 25^oC the standard enthalpy of formation of HXO4 (g) is -970.8 kJ/mol. The standard entropy of HXO₄ (g) and X(s) are, respectively 197.8 J/mol K and149.2J/mol K at 25^oC.Calculate the standard free energy change (kJ) for the following reaction at the 474K?    2HXO₄ (g) +7H₂ (g) → 2X(s) +8H₂O (g)