In the situation described in Exercise 1, how far should Anne run along the road if she wa...

In the situation described in Exercise 1, how far should Anne run along the road if she wants her trip to the helicopter to take the least possible amount of time?

Exercise 1

Anne is standing on a straight road and wants to reach her helicopter, which is located 2 miles down the road from her, a mile from the road in a field (see the figure). She can run 5 miles per hour on the road and 3 miles per hour in the field. She plans to run down the road, then cut diagonally across the field to reach the helicopter. If she runs less than a mile on the road and arrives at the helicopter in 42 minutes (.7 hour), exactly how far did she run on the road?