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. So we're asking about the distance between the car and the truck. So right at this moment when the car is 0.8 miles from the intersection, the truck is 0.6 miles from the intersection, the truck is traveling at 30 miles per hour towards the intersection, the car is traveling 60 miles per hour towards the intersection, right at this moment, what is the rate at which this distance right over here is changing? And just so that we have some variables in place, let's call this distance s. So what we really are trying to figure out is right at this moment, what is ds dt going to be equal to?