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