A. You would turn it into a fraction and divide the numeratoe by the denominator and the denominator by the denominator.
Ex.: 27,000/5000 divided by 5000 27000 becomes 5.4 and 5000 becomes 1 so $5.4/book.
B. Option A= $5.4/book
Option B= $4/book
Option C= $3.123.../book
So option C would be the best plan since it has the lowest cost per book!