$\"\"$

Choose any two points on the line and find the rate of change between them.

We will the points at (2, 1000) and (4, 2000).

(2, 1000) $\"\"$ 2h time, 1000mi distance.

(4, 2000) $\"\"$ 4h time, 2000 distance. $\"\"$

Rate of change = $\"\"$ .

The distance changes from 1000mi to 2000mi and the time changes from 4h to 2h.

Rate of change = $\"\"$

Rate of change = $\"\"$ . (Divide: $\"\"$ )

So, the rate of change is $\"\"$ , or a increase of 250mi per one hour. $\"\"$

The rate of change is $\"\"$ .