Answer:
[tex]{\text{C. }603.3\:\mathrm{miles}[/tex]
Step-by-step explanation:
The Law of Cosines works for any triangle and can be used to solve a triangle when we are given two sides and the angle between them.
Letting the missing side be [tex]c[/tex]:
[tex]c^2=a^2+b^2-2ab\cos C,\\c^2=400^2+250^2-2\cdot 400\cdot 250\cdot \cos135^{\circ},\\c^2=363921.356237,\\c=603.258946256\approx \boxed{\text{C. }603.3\:\mathrm{miles}}[/tex]
