So pause this video again and try to do what we just did with the previous example. Write out that interpretation, and make sure to get the units right. All right, so let's just remind ourselves what's going on. V is going to give us the volume as a function of time. Volume is in liters, and time is in minutes. And so if they're talking about the slope of the tangent line to the graph, the slope of the tangent line to the graph of v, that's just v prime. So if you take the derivative with respect to time, that's going to give you v prime, and these are all functions of t. These are all functions of t. And they say at t equals seven, it's equal to negative three.