So we also know what s is. So let's substitute all of these numbers in and then try to solve for what we came here to do, solve for ds dt. So the rate at which 2 times x, maybe I'll do that in yellow, 2 times x, x is 0.6, is going to be 1.2 times dx dt. So that's negative 30 miles per hour. So times negative 30 miles per hour plus 2 times y is 1.6, times dy dt is negative 60 miles per hour. And I'm not writing the units here, but if you were to write the units, you will see that all of our distances are in miles and all of our time is within hours. So we're going to get an answer when we solve for ds dt.