Henry: I wanna ask about the offer
Fiona: Hello, I'm Fiona. How can I help you?
Henry: can you tell me the detials about the black friday sale
Fiona: Certainly, You get 20% off on the first item, 40% on the 2]secound item and 70% off on the third item
Henry: What about the 4th?
Fiona: The sale only pertains to the first three items that you buy
Henry: ok, which items though? there has to be a hook
Fiona: I don't understand
Henry: Like it has to be the 3 least expensive items or something like that
Fiona: If you buy more than 3 items the sale will only pertain to the 3 least expensive ones
Henry: Ha! knew it!
Fiona: and the sales will be added on to the items according to price, from hte most expensive item to the least expensive one
Henry: well that sukcs 
The offer Henry is interested in concerns only 3 least expensive items.