TI-84 Graphing Histograms with Unequal Class Intervals

I'm unsure where to post this, let me know if it is suited for a different forum.

If I was graphing a histogram from a frequency table of grades with intervals like 90-100 (A), 80-89 (B), 70-79 (C), 60-69 (D), <60, then how would I set the intervals on the calculator to graph an accurate diagram. Currently Xscl seems to only allow one value for all intervals. Is it there a way to set the early one's to 10 then 9 then anything less than 60? Additionally, if the min is <60 then would I start at 0 and have the max be 100? Overall, I do not know how to graph a histogram with the above intervals on a graphing calculator.

How would I make the interval include values from 90-100 instead of min = 90 and max < 100? I want max = 100. Then, how would I make <60 have min = 0 and max < 60? How do I make sure these conditions are true while also having the middle intervals set properly?

Any help would be appreciated, thanks.
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