A Certain Factory Whistle Can Be Heard Up to a Distance

Multiple Choice

A certain factory whistle can be heard up to a distance of 9.8 km. Assuming that the acoustic output of the whistle is uniform in all directions, at what distance from the factory is the intensity level of the whistle sound equal to 25 dB? The threshold of human hearing is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

A) 940 m
B) 1100 m
C) 830 m
D) 550 m
E) 660 m