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 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

A) 2.6 mW
B) 0.026 mW
C) 0.079 mW
D) 0.26 mW
E) 0.79 mW