Answer: 412.310 miles
Explanation:
The diagram representing the scenario is shown in the attached photo. The bearing is taken with respect to the northern direction. The angles at B are determined by applying the concept of alternate angles with respect to parallel lines.
A right angle triangle ABC is formed. The starting point is A and the end point is C. The distance, x between A and C represents the hypotenuse of the triangle.
We would determine x by applying Pythagoras theorem which us expressed as
Hypotenuse² = opposite side² + adjacent side²
x² = 400² + 100² = 170000
x = √170000
x = 412.310 miles