If you look at Desmos you will see that when you put in the (x,y) coordinates in the x,y positions in your inequality that lines your plot and the shaded areas are different. If you put in each of the coordinates in the inequality you will see all the differenences between the shaded and the lines. I would do that in Desmos and you should be able to figure it out. There is an example picture below.
I hope this helps!
If you have any questions or need any help, please ask.
If the book stores sells 5 books for 27.25, then 1 book costs 27.25/5=5.45 the online store sells one book with the price of 32.16/6=5.36 the online store has a lower unit price