CHM220H1 Lecture 9: CHM220 Lecture 9- 2nd Law of Thermodynamics

I am suppose to find the buffering regions on this graph of aweak acid mixed with a strong base. But I m not sure how to findthe buffer regions. Any help would be great! I have to drawhorizontal lines of where the buffer regions end and start.

Thanks!

help! i don't know how to calculate the ph at the buffer regions. the question is: sketch a ph titration curve describing titrating 75. ml of .137 M H3PO4 with .275 M KOH identify buffer regions and ph at each buffer region