A Radio Transmitter Is Operating at an Average Power Of 4.00

A radio transmitter is operating at an average power of $4.00 \mathrm {~kW}$ and is radiating uniformly in all directions. What is the average intensity of the signal $8.00 \mathrm {~km}$ from the transmitter?

A) $2.49 \mu \mathrm { W } / \mathrm { m } ^ { 2 }$
B) $0.00497 \mathrm {~W} / \mathrm { m } ^ { 2 }$
C) $0.00249 \mathrm {~W} / \mathrm { m } ^ { 2 }$
D) $4.97 \mu \mathrm { W } / \mathrm { m } ^ { 2 }$