A Bat Emits a Sound at a Frequency of 30

Multiple Choice

A bat emits a sound at a frequency of 30.0 kHz as it approaches a wall.The bat detects beats such that the frequency of the echo is 900 Hz higher than the frequency the bat is emitting.The speed of sound in air is 340 m/s.The speed of the bat is closest to

A) 20.0 m/s.
B) 530 m/s.
C) 10.0 m/s.
D) 30.0 m/s.
E) 5.02 m/s.