The oxalosuccinate ⇌ α-ketoglutarate + CO2

reaction, starting from an oxalosuccinate solution, reaches equilibrium. The osmotic pressure was measured at the beginning of the reaction and after the equilibrium has been reached at T = 27 oC. The osmotic pressures are π0 = 0.049 atm. and πeq = 0.060 atm. What is the Gibbs free energy of the reaction if the total concentration of the products is 100 times greater than the concentration of the reactant?

I was not able to find an equation regarding this problem… I only understand between solutes and solvents