An eagle flying at 31 m/s emits a cry whose frequency is 440 Hz. A blackbird is moving in the same direction as the eagle at 16 m/s. (Assume the speed of sound is 343 m's.) (a) What frequency does the blackbird hear (in Hz) as the eagle approaches the blackbird? Hz (b) What frequency does the blackbird hear (in Hz) after the eagle passes the blackbird? Hz