Check correctness of histogram

I found this great activity for students to create a histogram, but I would like for it to be self-checking. It looks like there’s a .png image in the graph code, but it’s not linked to anything and I’m not sure how to check for correctness in a graph.

I added two folders in the graph. Answers and Correctness.
I_correct which is I subscript correct is the variable that gives the check in the graph.

Thank you, so much. This is perfect!!