First draw a picture - see attachment.

Then the required distance is twice the hypotenuse of a right triangle

with sides of 6 and 8. You can use Pythagoras's theorem to compute

this. Or you can observe that 6 and 8 are twice the sides of a 3,4,5

triangle so the hypotenuse you seek is 10 mile, and so the total distance

is 20 mile.

Method 2: This is a multiple choice question. Therefore do a scale diagram

and measure the distance of off the diagram.

RonL