This is 10x, this is 10x minus all of this business. So minus x to the third plus 6x squared minus 15x. I just subtracted x squared. You subtract a 6x squared, it becomes positive. You subtract a 15x, it becomes negative 15x. And then we can simplify this as, let's see, we have negative x to the third plus 6x squared minus 15x plus 10x, so that is minus 5x. Now if we want to optimize this profit function analytically, the easiest way is to think about what are the critical points of this profit function and are any of those critical points minimum points or maximum points?