Labeling endpoints on a histogram (can add or remove columns is necessary)

In this case, we'll have to carry out several steps to find the solution.
Step 01:
data:
hearing experiment:
25, 22, 18, 35, 37, 34, 27, 36, 36, 36, 33, 33, 30, 30, 26
Step 02:
histogram:
we must analyze the data to find the solution.
general histogram:
[tex][/tex]