Biomolecules, enzyme kinetics

Triose phosphate isomerase converts dihydroxy acetone phosphate (DHAP) to glyceraldehyde-3- phosphate (G-3-P) in a reversible reaction. At 298 K and pH 7.0, the equilibrium mixture contains 40 mM DHAP and 4 mM G-3-P. Assume that the reaction started with 44 mM DHAP and no G-3-P. The standard free-energy change in kJ/mol for the formation of G-3-P [R = 8.315 J/mol.K] is _________.