So the fact that the second derivative is less than zero, that means that my derivative is decreasing, my derivative, my first derivative is decreasing when x is equal to this value, which means that our graph, our function is concave downwards here. Concave, concave downwards. And concave downwards means it looks something like this. And so, and you can see when it looks something like that, the slope is constantly decreasing. So if you have an interval where the slope is decreasing and you know the point where the slope is exactly zero, which is where x is equal to 3.528, it must be a maximum. It must be a maximum. So we actually do take on a maximum value when x is 3.528.