So x cannot be 12.74. So we get a critical point at x is equal to 3.92. And you could look at the graph, and you could say, oh look, that looks like a maximum value. But if you didn't have the graph at your disposal, you can then do the second derivative test and say, hey, are we concave upwards or concave downwards when x is equal to 3.92? Well, in order to do the second derivative test, you have to figure out what the second derivative is, so let's do that. V prime prime of x is going to be equal to, is going to be equal to 24x, 24 times x to the first, minus 200. Minus, minus 200.