Hi! help please! A book sits motionless on a table. Which statement is true?

The upward force is greater than the downward force on the book.
There are no forces acting on the book.
The forces acting on the book are balanced by each other.
The downward force is greater than the upward force on the book.

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.