As a library manager, you are tasked with organizing a bookshelf alphabetically according to the author's last name. Given the nature of the job, you only have a litf:le trolley to aid you in organizing the books since the bookshelf is completely full.

If space was not a problem on the trolley, how much trolley space $($e$.$g$.$ additional memory slots$)$ would be needed for you to perform the insertion sort algorithm?

One more than the number of books on the bookshelf.

Half of the number of books on the bookshelf.

Twice the number of books on the bookshelf.

One memory slot

The same as the number of books on the bookshelf.