And right now, right at this moment, it is 0.8 miles from the intersection. Now we have this truck over here. It's approaching the same intersection on a street that is perpendicular to the street that the car is on. And right now it is 0.6 miles. So that is 0.6 miles from the intersection and is approaching the intersection at 30 miles per hour. Now my question to you is, what is the rate at which the distance between the car and the truck is changing? Well, to think about that, let's first just think about what we're asking.