## Algebra 2 (1st Edition)

$10.8$ miles.
Let it enter the layer at $(x_1,-4)$ and leave at $(x_2,-4)$. Then $x_1^2+(-4)^2=15^2\\x_1^2=209\\x_1\approx\pm14.6$ As we can see $x_1$ is negative, thus $x_1=-14.6$. $x_2^2+(-4)^2=10^2\\x_1^2=84\\x_1\approx\pm9.2$ As we can see $x_1$ is negative, thus $x_2=-9.2$. Then the distance is: $|x_1-x_2|=|-14.6-(-9.2)|=5.4$ Since the figure is symmetric, it will cover the same amount of space in the fourth quadrant as well, thus the answer is: $2\cdot5.4=10.8$