Brown bats emit sonic waves at 110 decibels measured at 10 cm away. They detect the sound wave reflected by flying insects or obstacles in their flying path. In this problem, assume the wave has a frequency 30.0 kHz, and that the bat's hearing threshold is 20 dB (limited by the natural noise level). The speed of sound is 343 m/s. A. (12 pts) A brown bat flies toward a stationary bird at a speed of 7.0 m/s. What frequency does the bat hear in the reflected wave? (The reflection of the sound wave by the bird does not alter the frequency of the wave.) B. (8 pts) If the sound wave reflected off the stationary bird is isotropic, at what distance away from the bird would the bat be able to detect C. (2 pts) The bird senses the approaching bat and flies directly away at 5.0 m/s. What frequency will the bat detect now? Is it greater or less than the frequency the bat detected when the bird was stationary?