During Glycolysis, Glucose 1-Phosphate Is Converted to Fructose 6-Phosphate in Two

During glycolysis, glucose 1-phosphate is converted to fructose 6-phosphate in two successive reactions: glucose 1-phosphate $\rightarrow$ glucose 6-phosphate
$\Delta$ G'° = -7.1 kJ/mol
Glucose 6-phosphate $\rightarrow$ fructose 6-phosphate
$\Delta$ G'° = +1.7 kJ/mol
$\Delta$ G'° for the overall reaction is:

A) -8.8 kJ/mol.
B) -7.1 kJ/mol.
C) -5.4 kJ/mol.
D) +5.4 kJ/mol.
E) +8.8 kJ/mol.