If you have a building supply store that sells to both professional
and retail customers. The professional builders buy in much larger
volume but are very fussy about price.

How would you diagram and explain if you could use price
discrimination to maximize your profits?
In which market will you charge the higher price? Is there an economic
theory to justify this?
What can you use to segment the markets, to keep the low price buyer
from selling to the high priced one?