Let's match each expression with its units, and like always, pause the video and see if you can do it on your own. All right, so the first one is b prime of t. So this is the rate of change of which the base is changing with respect to time. So if we think about it, b of t, that is the base, that is going to be in meters. So this is going to be in meters. If we say b prime of t, this is going to be how much our base is changing with respect to time. So this is going to be meters per, and they give us right over here, they say it's decreasing at a rate of 13 meters per hour. So the units here are meters per hour.