When a Mixture of Glucose 6-Phosphate and Fructose 6-Phosphate Is $\rightarrow$

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase (which catalyzes the interconversion of these two compounds) until equilibrium is reached,the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate.Which one of the following statements is best applied to this reaction outlined below? (R = 8.315 J/mol·K;T = 298 K)
Glucose 6-phosphate $\rightarrow$ fructose 6-phosphate

A) ( $\Delta$ G'° is incalculably large and negative.)
B) ( $\Delta$ G'° is -1.72 kJ/mol.)
C) ( $\Delta$ G'° is zero.)
D) ( $\Delta$ G'° is +1.72 kJ/mol.)
E) ( $\Delta$ G'° is incalculably large and positive.)