A student made a sketch of a potential energy diagram to represent an exothermic reaction. A curve line graph is shown. The y axis of the graph has the title Potential Energy and kJ written in parenthesis. The x axis of the graph has the title Reaction Pathway. The curve begins at a lower level and ends at a slightly higher level. A broken horizontal line is shown from a point labelled X on the y axis to the point where the curve begins. Another broken horizontal line is shown from a point labeled Y on the y axis to the point where the curve ends.

Explain, using complete sentences, why the diagram made by the student is correct or incorrect. Be sure to also explain what the values of X and Y represent.