Interstates 1-35 and 1-80 intersect near Ankeny. At 8 AM, Bob starts driving from Des Moines which is 10 miles south of the intersection point. He drives north along I-35 at 60 miles per hour. Alice also starts driving at 8 am, from a point 10 miles east of the intersection. She drives west along 1-80 at 80 miles per hour. How close do Bob and Alice get to each other? The closest that Bob and Alice get to each other is miles.