How a complement changes

A library initially considers books numbered 1 to 8, so \(\xi=\{1,2,\ldots,8\}\). The borrowed books form \(A=\{2,5,8\}\). Later, books 9 and 10 are added to the collection and neither is borrowed.

1. List \(A'\) before the two books are added.[1]
2. List \(A'\) in the enlarged universal set.[1]
3. Explain why \(n(A)\) is unchanged but \(n(A')\) increases.[1]