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

Multiple Choice

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is MOST correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K) ?
Glucose 6-phosphate $\harr$ fructose 6-phosphate

A) " $\Delta$ G ^' $\degree$ is +1.7 kJ/mol."
B) " $\Delta$ G ^' $\degree$ is -1.7 kJ/mol."
C) " $\Delta$ G ^' $\degree$ is zero."
D) "It is not possible to calculate $\Delta$ G ^' $\degree$ "