In a typical reaction coordinate diagram, the activation energy of a reaction is represented by the energy barrier that must be overcome for the reaction to proceed. In the case of a catalyzed reaction, the activation energy is usually lower than that of an uncatalyzed reaction.
To identify the activation energy of the catalyzed reaction from your graph, look for the energy difference between the reactants (starting energy level) and the peak of the curve (the transition state) in the section representing the catalyzed pathway.
Since I can't see the graph, I can only guide you through the process. You should look for the following:
- The starting point of the reactants on the left.
- The peak of the curve corresponding to the transition state.
- The difference in energy (height) between these two points represents the activation energy.
If one of the letters (a, b, c, or d) corresponds to this energy difference in the catalyzed reaction pathway, that letter represents the activation energy you're seeking.