When the slope is decreasing the entire time, our shape looks like that. The slope could start off high, lower, lower, gets to zero, even lower, lower, lower. And we even saw that on the graph right over here. And since it's concave downwards, that implies that our critical point that sits where, during where the interval is concave downward, that critical point is a local maximum, is a maximum. So this is the x value at which our function attains our maximum. Now, what is that maximum value? Well, we could type that back in into our original expression for volume to figure what that is.