When A is loaded into a cylinder at 9.89 atm and the system

Consider the equilibrium
A ( g ) ⇀↽ 2 B ( g ) + 3 C ( g )
at 25◦C. When A is loaded into a cylinder at 9.89 atm and the system is allowed to come to equilibrium, the final pressure is found to be 15.94 atm. What is ∆G◦r for this reaction?
Answer in units of kJ/mol