A plane flies at 200 mph for the first and last half hour of a flight. It flies at 400 mph the rest of the time. The route is 1000 miles long. The town of Erehwon is on the route 300 miles before the end. What is the distance of the plane from Erewhon after t hours of flying?

t≤12 =  ?miles
1/2≤t≤2 =  ?miles
2≤t≤2 1/2 = ? miles
2 1/2≤t≤3 =? miles