Answer:
-20 kcal/mol
Explanation:
In a reaction, enzymes reduces the energy of activation, but they have no effect on the Gibb's free energy of reaction. The free energy of the product is the same as it would be without the enzyme. Thus, the enzyme does not affect the free energy of the reaction. Mathematically
Gibb free energy = Enthalpy - temperature x change in entropy
Note that from the relation above, enzyme is not a factor nor is activation energy a factor.