Two students are working together on a project. One student applies for to a book to move it across the table to the other person. Student 1 applies the force of 20 N to push the book to student 2. If the force of friction resisting is 4, what is the net force acting on the book.
 A. 6 N
 B. 10 N
 C. 24 N
 D. 16 N