Answer
$$ A= 3043 \ mi^2$$
Work Step by Step
We find the area covered by each radio:
$$ A_1 = \pi (35\ mi)^2 \\ A_1 = 3847\ mi^2$$
And:
$$A_2 = \pi(16\ mi)^2 \\ A_2 = 804 \ mi^2$$
Thus, the difference is:
$$ A = 3847 \ mi^2 - 804\ mi^2 \\ A= 3043 \ mi^2$$
