A train sounds its horn as it approaches an intersection. The horn can just be heard at a level of 54 dB by an observer 10 km away. Treat the horn as a point source and neglect any absorption of sound by the air.
(a) What is the average power generated by the horn?
W
(b) What intensity level of the horn's sound is observed by someone waiting at an intersection 48 m from the train?
dB