A two-step mechanism proceeds as follows:
• Step 1 converts the reactants (0 kJ reference) to an intermediate at +45 kJ.
• Step 2 converts the intermediate to products at −60 kJ (all energies relative to the reactants).
Which option correctly classifies each step and the overall reaction?
a) Step 1 is endothermic, Step 2 is exothermic, overall reaction is endothermic.
b) Step 1 is endothermic, Step 2 is exothermic, overall reaction is exothermic.
c) Step 1 is exothermic, Step 2 is endothermic, overall reaction is exothermic.
d) Step 1 is endothermic, Step 2 is endothermic, overall reaction is endothermic.