The Standard Free-Energy Changes for the Reactions Below Are Given $\rightarrow$

The standard free-energy changes for the reactions below are given.
Phosphocreatine $\rightarrow$ creatine + P_i $\Delta$ G'° = -43.0 kJ/mol
ATP $\rightarrow$ ADP + P_i $\Delta$ G'° = -30.5 kJ/mol
What is the overall $\Delta$ G'° for the following reaction?
Phosphocreatine + ADP $\rightarrow$ creatine + ATP

A) -73.5 kJ/mol
B) -12.5 kJ/mol
C) +12.5 kJ/mol
D) +73.5 kJ/mol
E) ( $\Delta$ G'° cannot be calculated without K_eq'.)