According to the sorting instructions, you should first determine the correct cart for the book coded PN 225. Since it does NOT have a yellow dot, it should be placed on the gray cart.
Next, when sorting the books, we first look at the letter codes. Both PN 225 and PN 220 start with the same letters (PN), so we will then compare the numbers.
Since 225 is greater than 220, this means PN 225 should be placed after PN 220.
Now, let's analyze the options:
A. Before a book coded NP 220 - Incorrect, PN comes before NP. B. Before a book coded NP 230 - Incorrect, PN comes before NP. C. Before a book coded PN 220 - Incorrect, PN 225 comes after PN 220. D. After a book coded PN 220 - Correct, PN 225 comes after PN 220. E. After a book coded PN 230 - This cannot be determined without more information about the relation between PN 225 and PN 230.
The correct answer is D. After a book coded PN 220.