At 25 ∘ C , the equilibrium partial pressures for the reaction 3 A ( g ) + 2 B ( g ) − ⇀ ↽ − C ( g ) + 2 D ( g ) were found to be P A = 4.87 atm, P B = 4.37 atm, P C = 5.95 atm, and P D = 5.36 atm. What is the standard change in Gibbs free energy of this reaction at 25 ∘ C ?