So this is going to be 30 minus two x. So now we have all of the dimensions. So what would the volume be as a function of x? Well, the volume as a function of x is going to be equal to the height, which is x, times the width, which is 20 minus two x, times the depth, which is 30 minus two x. Now what are possible values of x that give us a valid volume? Well, x can't be less than zero. You can't make a negative cut here.