Instructions: You are given a math word problem and you are supposed to apply multiplication or division mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
Input: Bianca was organizing her book case making sure each of the shelves had exactly 8 books on it . If she had 5 shelves of mystery books and 4 shelves of picture books , how many books did she have total ?
Output:
72